498

Epifanio BEYES, Individually and as next Friend of Anita Beyes, a minor, Plaintiff-Appellee, v.

WYETH LABOBATOEIES, a Division of American Home Products Corporation, a Delaware corporation, Defendant-Appellant. No. 72-2251.

United States Court of Appeals, Fifth Circuit. July 31, 1974.

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126

Loyd E. Bingham, Jr., San Antonio, Tex., Eberle, Berlin, Kading, Turnbow & Gillespie, R. B. Kading, Jr., William J.

McElveen, Boise, Idaho, for defendantappellant.

Daniel R. Murray, Chicago, 111., for American Academy of Pediatrics, amicus curiae.

William J. Curran, Boston, Mass., for Conference of State and Territorial Epidemiologists, amicus curiae.

Rafael H. Flores, J. Perry Jones, McAllen, Tex., for plaintiff-appellee.

Before BROWN, Chief Judge, and WISDOM and AINSWORTH, Circuit Judges.

WISDOM, Circuit Judge: This products liability case raises significant questions concerning the scope of a drug manufacturer's duty to warn ultimate consumers of dangers inherent in his product.

In May 1970, slightly more than two weeks after she had received a dose of Wyeth Laboratories' oral polio vaccine, eight-month-old Anita Reyes was diagnosed as having paralytic poliomyelitis. Epifanio Reyes, Anita's father, filed suit against Wyeth Laboratories, alleging that the live polio virus in the vaccine had caused Anita's polio and that Wyeth was liable for her injuries because it had failed to warn her parents of this danger. Wyeth contends that it is not liable for Anita Reyes's injuries under the products liability law of Texas. In addition, Wyeth raises numerous procedural and evidentiary questions. The case was tried to a jury. The jury answered special interrogatories (see Appendix A) and returned a verdict in favor of Reyes against Wyeth for the sum of $200,000.

I.

Twenty or thirty years ago poliomyelitis was a dread disease that especially attacked the very young. In 1952 alone, there were 57,879 reported cases of polio in the United States; 21,269 of these resulted in crippling paralysis to the victims. By 1970, when Anita Reyes contracted polio, the number of those stricken by polio had diminished dramatically; she was one of just 33 individuals to be

afflicted during that year.^{Footnote 1} Credit for this precipitous decline must go primarily to the medical researchers who discovered the viral nature of the disease, and were able to isolate and reproduce the virus in an inactivated or an attenuated form. See Appendix B. But credit for this remarkable achievement must also be given to such laboratories as Wyeth, which processed the polio vaccine, and to massive federal-state public health programs for the administration of the vaccine.

On May 8, 1970, Anita Reyes was fed two drops of Sabin oral polio vaccine by eye-dropper at the Hidalgo County Department of Health clinic in Mission, Texas. The vaccine was administered to Anita by a registered nurse; there were no doctors present. Mrs. Reyes testified that she was not warned of any possible danger involved in Anita's taking the vaccine. Mrs. Reyes has a seventh grade education, but her primary language is Spanish. She signed a form releasing the State of Texas from "all liability in connection with immunization". The form contained no warning of any sort, and it is apparent from her testimony that she either did not read the form or lacked the linguistic ability to understand its significance. About fourteen days after the vaccine was administered, Anita Reyes became ill. On May 23, 1970, she was admitted to the McAllen (Texas) General Hospital, where her disease was diagnosed as Type I paralytic poliomyelitis. See Appendix B, footnote 59. As a result of the polio, at the time of trial Anita was completely paralyzed from the waist down, her left arm had become atrophied, and she was unable to control her bladder or bowel movements.

The vaccine given Anita Reyes in the Mission clinic on May 8, 1970 was part of a "lot", No. 15509, prepared by Wyeth.* Lot No. 15509 was trivalent oral polio vaccine that Wyeth had titered (mixed) from Types I, II, and III monovalent vaccine provided by Pfizer, Ltd. In response to an order placed by the Texas State Department of Health on December 23, 1969, Wyeth shipped 3500 vials of Lot No. 15509 vaccine to the State Health Department which in turn transferred 400 vials to the Hidalgo County Health Department. The jury found that vaccine from one of these vials was given to Anita Reyes. Included with every vial, each of which contained ten doses of vaccine, was a "package circular" provided by Wyeth which was intended to warn doctors, hospitals, or other purchasers of potential dangers in ingesting the vaccine. Mrs. Lenore Wiley, the public health nurse who administered the vaccine to Anita Reyes, testified that she had read the directions on this package insert, but that it was not the practice of the nurses at the Mission Health Clinic to pass on the warnings to the vaccinees or to their guardians. She testified that she gave Mrs. Reyes no warning before she administered the vaccine to Anita.

On October 7, 1970, Epifanio Reyes, individually and as next friend of his minor daughter, brought this action on theories of strict products liability, breach of warranty, and negligence. In his complaint he alleged that his daughter had contracted polio from the live virus in Wyeth's vaccine, and that Wyeth's failure to warn him or his wife that this might occur rendered it liable for Anita's injuries. Wyeth's main line of defense was that Anita's polio was

not vaccine-induced at all. Wyeth produced experts who characterized virus isolated from a specimen of stool taken from Anita on the day after she was admitted to the hospital as "probably wild". This probability was increased, according to epidemological testimony adduced on Wyeth's behalf,^{Footnote 3} by the fact that there was a polio "epidemic" in Hidalgo County at the time Anita fell ill. In effect, the jury rejected these theories in rendering a verdict for Reyes. Wyeth asserts more than a score of separate grounds for reversal, each accompanied by extensive argument and citation. We have considered all of these contentions, but in this opinion we shall address only those challenges which we regard as raising substantial questions.

II.

We turn first to the substantive issues raised by this appeal. Our inquiry is bounded by the jury's finding that Wyeth's vaccine was the producing cause of Anita Reyes's polio, and by those principles of products liability law we conclude would be applied by the courts of Texas. Erie R. R. Co. v. Thompkins, 1938,  304 U.S. 64, 58 S.Ct. 817, 82 L.Ed. 1188.

The jury's finding that the Wyeth vaccine was responsible for Anita Reyes's polio is less a conclusion than a starting point. Texas courts may hold manufacturers of products which harm consumers liable for the injuries, but, of course, manufacturers are not insurers. ^{Footnote 4}

Texas courts recognize both tort and warranty theories of products liability. ^{Footnote 8}

This case was tried, briefed, and argued on appeal entirely on the tort theory of strict liability. Thus the differences between the two approaches,* and whatever contractual trappings of warranty have not been destroyed with the crumbling of the citadel of privity,'¹ need not detain us. Rather, we turn to the theory of strict products liability as embodied in Section 402A of the Restatement (Second) of Torts (1965), 8 and approved

by the Supreme Court of Texas in McKisson v. Sales Affiliates, Tex.Sup.Ct. 1967, 416 S.W.2d 787. ^{Footnote 9}

Basically, Section 402A subjects to liability the seller or manufacturer of a product sold "in a defective condition unreasonably dangerous" to an ultimate user or consumer whose person or property is physically harmed by the product. ^{Footnote 10}

Moreover, one who places defective goods in the stream of commerce will be liable "to the user or consumer even though he has exercised all possible care in the preparation and sale of the product". Eestatement (Second) of Torts, Section 402A, comment a. Yet imposition of liability is by no means automatic; the elements tacit or explicit in Section 402A's mandate must be demonstrated to the trial court's satisfaction before the burden of the consumer's loss will be imposed on the seller of the product: The plaintiff is faced with an arduous burden of proof. He must prove that: 1) the product in question was defective ; 2) the defect existed at the time the products left the hands of the defendant; 3) that because of the defect the product was unreasonably dangerous to the user or consumer (plaintiff) ; 4) that the consumer was injured or suffered damages; 5) and that the defect (if proved) was the proximate cause of the injuries suffered. Gravis v. Parke-Davis & Co., Tex.Civ. App.1973, 502 S.W.2d 863, 868. Although we do not embrace Gravis as the all-inclusive embodiment of Texas products liability law, the framework it provides suggest a useful analysis for the issue of Wyeth's liability here.

All five elements, however, which constitute the Gravis requirements need not be discussed here. There can be no question that Anita Reyes was injured, so the fourth element is not in issue. Nor is the second, since the defect alleged, failure to warn by the manufacturer, is by definition the manufacturer's dereliction. Moreover, to find that the plaintiff proved the first element is to conclude that he proved the third, for properly understood, "defective condition" has no meaning independent of "unreasonably dangerous"; the two terms are essentially synonymous. ^{Footnote 11}

Thus if a product is unreasonably dangerous as marketed, the manufacturer may be held liable for injuries proximately caused by what he has produced, whether or not it was manufactured exactly as intended, that

is without a production "defect".

18 do not understand this approach to dispense with the principle that to prompt liability a product must reach the consuming public in a "defective condition". Eather, by rephrasing the defectiveness requirement in terms of "unreasonable danger", it becomes clear that the circumstances of marketing themselves can amount to a defect; the defect can be extrinsic to the product. All that we need determine here, then, is first, whether the vaccine was unreasonably dangerous, and second, whether the showing of proximate causation was sufficient under Texas law. a) Unreasonable Danger and the Duty to Warn

We begin the inquiry by asking whether the vaccine was unreasonably dangerous, that is, in a defective condition when Anita Reyes received it. It is clear, of course that the vaccine was not itself defective. Wyeth Vaccine Lot No.

15509 was exactly what its makers ^{Footnote 13} and the Texas public health authorities intended it to be: trivalent live-virus Sabin oral polio vaccine. The live virus which the jury concluded caused Anita's poliomyelitis was not inadvertently included in the mixture.

14

Indeed, it is the presence of the living but attenuated Type I, II, and III viruses which makes the Sabin vaccine so effective [See Appendix B].

Although the living virus in the vacWe cine does not make the vaccine defective, it does make it what the Restatement calls an "unavoidably unsafe product", one which cannot be made "safe" no matter how carefully it is manufactured. Such products are not necessarily "unreasonably dangerous", for as this Court has long recognized in wrestling with product liability questions, many goods possess both utility and danger. See, e. g., Ross v. Up-Right, Inc., 5 Cir. 1968,  402 F.2d 943, 946; Helene Curtis Industries, Inc. v. Pruitt, 5 Cir. 1967,  385 F.2d 841, 850, cert, denied, 1968, 391 U.S. 913, 88 S.Ct. 1806, 20 L.Ed.2d 652. Rather, in evaluating the possible liability of a manufacturer for injuries caused by his inevitably hazardous products, a two-step analysis is required to determine first, whether the product is so unsafe that marketing it at all is "unreasonably dangerous per se", and, if not, whether the product has been introduced into the stream of commerce without sufficient safeguards and is thereby "unreasonably dangerous as marketed" ^{Footnote 15} . In either case, the applicable standard, as formulated in the Restatement, is as follows: In terms of the user's interests, a product is "unreasonably dangerous" only when it is "dangerous to an extent beyond that contemplated by the ordinary consumer"; ^{Footnote 16} or, to phrase it in terms of the seller's responsibility, "so dangerous that a reasonable man

would not sell the product if he knew the risk involved". See Borel v. Fibreboard Paper Products Corp., 5 Cir. 1973,  493 F.2d 1076, 1088; Helene Curtis Industries, Inc. v. Pruitt, 385 F.2d at 850; Wade, Strict Tort Liability of Manufacturers, 19 Sw.L.J. 5, 15 (1965).

In determining whether placing a commodity on the market is "unreasonably dangerous per se", the reasonable man standard of the Restatement becomes the fulcrum for a balancing process in which the utility of the product properly used is weighed against whatever dangers of harm inhere in its introduction into commerce. Obviously, use of an unavoidably unsafe product always presents at least a minimal danger of harm, but only if the potential harmful effects of the product' both qualitative and quantitative'outweigh the legitimate public interest in its availability will it be declared unreasonably dangerous per se and the person placing it on the market held liable.

11 Applying this standard here, the scales must tip in favor of availability. The evil to be prevented'poliomyelitis and its accompanying paralysis'is great.

Although the danger that vaccinees may contract polio is qualitatively devastating, it is statistically miniscule. On balance then, marketing the vaccine is justified despite the danger.

Since Sabin oral polio vaccine is not "unreasonably dangerous per se", we move to the second step of our analysis to determine whether it is "unreasonably dangerous as marketed", for to conclude that the maker of an unavoidably unsafe product did not act unreasonably in placing it on the market is not to relieve him of the responsibility to market it in such a way as to prevent unreasonable danger. In the case of a product such as Sabin oral polio vaccine, this translates into a duty to provide proper warnings in selling the product. As comment k to Section 402A instructs, an unavoidably unsafe product is neither defective nor unreasonably dangerous if ' such a product is "properly prepared, and is accompanied by proper directions and warning". ^{Footnote 18}

Consequently, the Ke-

statement requires a seller who has reason to believe that danger may result from a particular use of his product to provide adequate warning of the danger in order that the product's potential for harm may be reduced. Failure to give such a warning when it is required will itself present a "defect" in the product and will, without more, cause the product to be "unreasonably dangerous as marketed". ^{Footnote 19}

Issue is joined then, on the question whether Wyeth was under a duty to warn the parents of Anita Reyes that there was a possibility, however remote, that she might contract polio from the drug designed to immunize her. If such a duty existed, the vaccine was "defective" and unreasonably dangerous as marketed, for such cautions as Wyeth advanced did not, and were not intended to, reach the Reyes family. See Davis v. Wyeth Laboratories, Inc., 9 Cir. 1968,  399 F.2d 121, 129.

Wyeth does not deny that its vaccine is "unavoidably unsafe", or contend that it was unaware of the danger. Rather, the appellant contends that if it had a duty to warn at all, that duty was discharged by the warning contained on the package insert which accompanied the vials of vaccine sold to the Texas State Department of Health. This is so, Wyeth asserts, because the Sabin trivalent oral polio vaccine in issue here is a "prescription drug", and those who prepare such drugs are not required to warn the ultimate consumer. If the warning to the dispensing physician or authorities (here the Texas and Hidalgo County Public Health Departments) was adequate, Wyeth is not liable for any harm caused by the vaccine. Resolution of these contentions is crucial; Wyeth concedes in its brief that "[sjinee it is undisputed that Wyeth did not warn Reyes, but only the Texas State Department of Health, a finding that the vaccine was not a prescription drug estab-

lishes as a matter of law the defectiveness of the vaccine for purposes of a prima facie case in strict products liability." f We cannot quarrel with the general proposition that where prescription drugs are concerned, the manufacturer's duty to warn is limited to an obligation to advise the prescribing physician of any potential dangers that may result from the drug's use.

80

This special standard for prescription drugs is an understandable exception to the Restatement's general rule that one who markets goods must warn foreseeable ultimate users of dangers inherent in his products. See Restatement (Second) of Torts, Section 388 (1965). Prescription drugs are likely to be complex medicines, esoteric in formula and varied in effect. As a medical expert, the prescribing physician can take into account the propensities of the drug, as well as the susceptibilities of his patient. His is the task of weighing the benefits of any medication against its potential dangers. The choice he makes is an informed one, an individualized medical judgment bottomed on a knowledge of both patient and palliative. Pharmaceutical companies then, who must warn ultimate purchasers of dangers inherent in patent drugs sold over the counter, in selling prescription drugs are required to warn only the prescribing physician, who acts as a "learned intermediary" between manufacturer and consumer. ^{Footnote 21}

Although there is no question that Sabin oral vaccine is licensed for sale only as a prescription drug, 82 trict court, in its charge to the jury, noted that the vaccine was not administered as a prescription drug at the Mission Clinic. The court charged: "if you [the jury] find that a warning should have been given, the warning had to be given to Anita and her parents, not to Mrs. Wiley, that Public Health nurse, somebody else . . . The ultimate consumer is the one that had to be warned." The district court apparently based this instruction on the leading federal case in the area, Davis v. Wyeth Laboratories, 9 Cir. 1968,  399 F.2d 121. In Davis, the plaintiff had allegedly contracted polio from Wyeth oral vaccine distributed at a public clinic. The Ninth Circuit held that where no individualized medical judgment intervenes between the manufacturer of a prescription drug and the ultimate consumer, "it is the responsibility of the manufacturer to see that warnings reach the consumer, either by giving warning itself or by obligating the purchaser to give warning." 399 F.2d at 131. Where there is no physician to make an "individualized balancing ... of the risks", the Court reasoned, the very justification for the prescription drug exception evaporates. Thus, as in the case of patent drugs sold over the counter without prescription, the manufacturer of a prescription drug who knows or has reason to know that it will not be dispensed as such a drug must provide the consumer with adequate information so that he can balance the risks and benefits of a given medication himself. Moreover, just as the manufacturer cannot make this choice for its ultimate consumers, it cannot allow its immediate purchaser to choose for them. In sum, then, the manufacthe disturer is required to warn the ultimate consumer, or to see that he is warned. 399 F.2d at 131.

Wyeth does not resist the Ninth Circuit's holding in Davis, but asserts that the instant case can be distinguished on four grounds. First, the appellant argues, Davis received his vaccine during a mass immunization program, whereas Anita Reyes ingested her vaccine at her parents' request. Second, Wyeth stresses the fact that Davis received his vaccine from a pharmacist, but Reyes' was administered by a public health nurse. Third, Wyeth's active participation in the mass immunization program involved in the Davis case is contrasted to its relatively passive role here. Finally, Wyeth urges that unlike the situation in Davis, here it had no knowledge that the vaccine would not be administered as a prescription drug.

None of these asserted grounds for distinguishing Davis justifies a different result here. The first two arguments are admittedly distinctions between Davis and the instant controversy, but they have no bearing on the rationale of the Davis opinion. Whether vaccine was received during a mass immunization or an on-going program, whether it was administered by nurse or pharmacist, it was, in both these cases, dispensed without the sort of individualized medical balancing of the risks to the vaccinee that is contemplated by the prescription drug exception. The third and fourth asserted bases for distinguishing Davis from this case are essentially the same: Wyeth took no active part in the vaccination process here, and did not know that its vaccine would be dispensed without procedures appropriate for distribution of prescription drugs.

Were we to conclude that Wyeth neither knew nor had reason to know that its vaccine would be dispensed without prescription drug safeguards, we might be required to hold that the rationale in Davis is inapplicable here. But Wyeth had ample reason to foresee the way in which its vaccine would be distributed. A drug manufacturer is held to the skill of an expert in his field, and is presumed to possess an expert's knowledge of the arts, materials, and processes of the pharmaceutical business.

83

Included in such expertise must be a familiarity with practices and knowledge common in the drug industry as to distribution and administration of pharmaceutical products.

Neal Nathansoii, Professor of Epidemiology at the Johns Hopkins University School of Public Health and a witness for Wyeth testified that it was common knowledge in the drug industry that "a great majority" of vaccinees receive their Sabin vaccine in mass administrations or county clinics manned at least in part by volunteers. Moreover, Dr. Nathanson agreed that it was well known that such clinics were stocked primarily by sale of vaccine to state health departments. These clinics, as Wyeth must be presumed to know, dispense Sabin vaccine to all comers in an "assembly line" fashion; there is often neither time nor personnel to make an "individualized medical judgment" of the vaccinee's needs or susceptibilities. See Davis v. Wyeth, supra, 399 F.2d at 131; 56 Geo.L.J. 1016, 1017 (1968); 5 San Diego L.Rev. 422, 428 (1968).

Viewed in this light, the present controversy, however it differs from Davis factually, invites application of the Davis principles, and the conclusion that Wyeth was under a duty to warn Anita Reyes's parents of the danger inherent in its vaccine. Wyeth knew or had reason to know that the vaccine would not be administered as a prescription drug, and therefore was required to warn foreseeable users, or see that the Texas Department of Health warned them. See Davis v. Wyeth, supra, 399 F.2d at 131; cf. Helene Curtis Industries v. Pruitt, SMpra, 385 F.2d at 861. Wyeth's failure to warn was a breach of its duty and made

the vaccine "defective"'hence "unreasonably dangerous"'as marketed.

Before moving to a consideration of causation, we pause to analyze two possible arguments, one raised by Wyeth and one not, which appear to add further conceptual problems in the "duty to warn" area.

The first may be disposed of quickly. Wyeth contends that whatever its duty to warn, Mrs. Eeyes assumed the risk that her daughter might contract polio, or effectively released Wyeth, by signing a "release" purporting to excuse the State of Texas from liability. Wyeth does not explain how signing a form releasing the State could excuse Wyeth from performing a duty to warn imposed on it by law, other than to cite the "unity of release" rule, apparently under the assumption that the State of Texas was its agent. Since we decline to adopt the district court's conclusion that Texas was the agent of Wyeth in administering the vaccine, we need not consider Wyeth's contention that the release signed by Mrs. Reyes also applied to it. Moreover, although we agree that assumption of risk is a proper defense to a product liability action in Texas (see Borel v. Fibreboard Paper Products Corp.) one cannot assume a risk of which he is unaware. Shamrock Fuel & Oil Sales Co. v. Tunks, Tex.Sup.1967, 416 S.W.2d 779, 786 and n. 8. Since Mrs. Reyes was not cognizant of the danger inherent in the vaccine, she could not have assumed the risk of its use.

Somewhat more troubling is a line of Texas cases involving unusual allergic reactions to potentially dangerous products sold without a warning. These decisions may be read for the proposition that only if the product, properly prepared, will harm a substantial number of people will the manufacturer be held liable for his failure to warn. See 0. A. Hoover & Son v. O. M. Franklin Serum Co., Tox.Sup.1969, 444 S.W.2d 596, 598; Alberto-Culver Co., v. Morgan, Tex.Civ.App.1969, 444 S.W.2d 770, 776777, writ ref. n. r. e.; Cudmore v. Richardson-Merrell, Inc., Tex.Civ.App. 1966, 398 S.W.2d 640, 644, 84 writ ref. n. r. e., cert, denied, 1967, 385 U.S. 1003, 87 S.Ct. 705, 17 L.Ed.2d 542.

Essentially these are foreseeability cases; the element they would require to invoke strict liability doctrines is foreseeability. In these cases, the manufacturer not only marketed the unavoidably unsafe product without adequate warning and with the knowledge that it was inherently dangerous, but the danger to any individual consumer was sufficiently significant and knowable that (1) the manufacturer was cognizant of a need to warn so as to prevent injury and (2) the consumer might or could have altered his conduct in such a way as to lessen or avoid the danger. This ancipital coin of foreseeability is the currency of these Texas cases. What they seek to avoid is the imposition of liability for "abreactions", hypersensitive allergic reactions so unique that the class of persons exposed to the risk is miniscule. See Cudmore v. Richardson-Merrell, Inc., 398 S.W.2d at 644. In such cases, warnings would be meaningless, since the manufacturer can convey nothing meaningful to the allergic consumer unless the latter knows he has the allergy. Without such knowledge, the consumer is apt to assume that he is not a member of the minute susceptible class and to disregard the warning. See Alberto-Culver Co. v. Morgan, 444 S.W. 2d at 777. Thus with the utility of warning limited and the susceptible class minute, the manufacturer is not required to foresee that anyone will suffer an allergic reaction to his product, and is not held liable.

To the instant analysis, these principles present no dilemma, for the effect

of the Sabin oral vaccine upon those who contract polio from it cannot fairly be styled an "abreaction".

23

Although the danger of vaccine-induced polio to any one individual is small, the risk appears to be distributed evenly among that substantial segment of the population that is not naturally immune to polio. This is so because the behavior of polio virus in those who contract the disease seems to suggest more a reversion to virulence by the virus than a sensitivity in the vaccinee. Thus, if an individual is a member of the significant susceptible class, and his case should be one of those rare instances in which the vaccine strain reverts to virulence, he may contract polio. This is not a case like Cudmore, then, where the "appellant belongs to a class of people not appreciable in number who are allergic to the drug," and in which a warning would have been futile. 398 S.W.2d at 644. Rather, proper warnings here would be addressed to a sizeable group and would be designed to alert each of its members that although the incidence of vaccineinduced polio is minute, he does belong to a substantial class, an unpredictible few of which could contract polio from the vaccine. In light of such factors, the Texas "abreaction" cases cannot dilute Wyeth's duty to warn here. This view coincides with the objective of Section 402A to protect the consumer by his standards of reasonableness in determining the manufacturer's duty. b) Proximate Cause

Having concluded that Wyeth had a duty to warn Anita Reyes, and that, dispensed without a warning, the vaccine was unreasonably dangerous, we now turn to Wyeth's objections to the trial court's not instructing the jury and not submitting an interrogatory on the issue of "proximate cause".

As Wyeth correctly contends, there are two causation issues in most product liability cases. The first is that of "producing cause": Was the defendant's product the cause-in-fact of the plaintiff's injuries? More specific is the question posed under the rubric of proximate causation: Did the plaintiff's injuries result from the alleged "defect" in the defendant's product? Unless the jury is given an opportunity to pass upon both issues, Wyeth urges, the plaintiff has not made out a prima facie case of product liability. If Wyeth is correct, reversal is required, for the trial judge made it clear that he did not believe proximate cause to be an issue in this controversy, and neither instructed the jury nor submitted an interrogatory on the question.

86 We cannot concur in

Wyeth's premise, however. The submission of interrogatories accompanying a general verdict is within the discretion of the trial court.

87

Moreover, although an instruction on proximate cause is appropriate in most products liability cases, a jury finding on the question was not required here.

As a general proposition, both Texas Courts and this Court have required that the plaintiff in a product liability suit prove not only that his injuries were caused by the defendant's product, but that they resulted from an alleged defect in the product. ^{Footnote 28}

commentators have concurred. ^{Footnote 29}

rule in Texas that proximate cause must be specifically proved in products liability cases is not immutable. In some circumstances, proximate cause may be inferred as a matter of law or as a matter of fact. Procter & Gamble Mfg. Co. v. Langley, Tex.Civ.App.1967, 422 S.W.2d 773, writ dismissed, want of jurisdiction. In other cases, an instruction on producing cause which omits a consideration of proximate cause may be sufficient. C. A. Hoover and Son v. 0. M. Franklin Serum Co., Tex.Sup.1969, 444 S.W.2d 596, 598. We believe, in light of the holding in Hoover and crucial dicta in Technical Chemical Co. v. Jacobs, Tex.Sup.1972, 480 S.W.2d 602, that to have omitted a specific proximate cause instruction here was not reversible error.

Hoover was an action against a serum manufacturer by the owners of 25 Hereford calves which had become desperately ill after having been innoculated with the defendant's antibiotic. The trial resulted in a verdict and judgment for the plaintiffs, which was reversed and remanded by the court of civil appeals because the trial court had submitted a special issue on "producing cause" rather than "proximate cause", "and had thus failed to require the element of foreseeability". The Supreme Court of Texas reversed the court of appeals, and held that where, as here, the injury's foreseeability was not in issue, the "producing cause" instruction was sufficient. Much of the Supreme Court's brief opinion is spent in distinguishing the issue presented in Hoover from that considered in Cudmore v. Richardson-Merrell, Leading Inc. Cudmore required that the jury Yet the consider whether the defendant's product was the "proximate cause" of the plaintiff's injuries rather than merely whether it was the "producing cause", since the latter inquiry "omits entirely the element of foreseeability. . . ." The Hoover court distinguished Cudmore on the ground that it involved an "abreaction" to a "pure drug" and thus foreseeability was a crucial issue. In such a case, a "proximate cause" instruction is required. In Hoover, however, all twenty-five innoculated cattle fell ill or died. The jury found that the cause of this widespread illness was not an unforeseeable abreaction. Thus, concluded the Texas Supreme Court, foreseeability was not in issue, and no proximate cause instruction was required.

The Hoover rationale is applicable to the instant controversy. Although this is, in a sense, a "pure drug" case like Cudmore, as we have pointed out above, it involves no "abreaction". As we have also concluded earlier, foreseeability' both as to the possibility of injuries and

the manner of dispensing the drug'is not really in issue. In Hoover, "foreseeability" was found by the jury; here it was established as a matter of law. Hoover was not, of course, a "failure to warn" case. The defect involved was intrinsic to the serum which felled the plaintiff's cattle, a fact which may differentiate Hoover from extrinsic defect cases where the product and defect are separable. See Keeton, Products Liability'Problems Pertaining to Proof of Negligence, 19 Sw.L.J. 26, 33 (1965). Yet language in Technical Chemical Co. v. Jacobs, the recent Texas Supreme Court examination of failure to warn, convinces us that even in this area, a producing cause instruction will suffice in the circumstances of this case.

Technical Chemical involved a suit against the manufacturer of a can of freon which exploded in the plaintiff's hand as he attempted to put its contents into the air conditioning unit of his automobile. It was apparent from testimony adduced at trial that Jacobs, the plaintiff, inadvertently and mistakenly attached a hose from the "high" pressure side of his air conditioning compresser to the can of freon, rather than joining a hose from the "low" pressure side, which was the proper procedure. The can exploded, a possible result which the directions on the can's label did not mention. Jacobs admitted, however, that he had not read the directions on the can's label. In light of this fact, the jury refused to find that Technical Chemical's failure to warn was a cause of Jacob's injuries.

In affirming the trial verdict, the Supreme Court of Texas held that it was "incumbent upon the plaintiff to secure a jury finding that the faulty labeling was a cause of the injury". This he had not done. 480 S.W.2d at 605. Moreover, a plaintiff who had not read such directions as were provided could hardly expect the court to conclude that the manufacturer's failure to provide further warnings caused his injury as a matter of law.

498 F.2d' 81 Although much of the Technical Chemical opinion speaks in absolute terms of requiring proof that the defect caused the plaintiff's injuries, it also recognizes how "speculative" testimony in this type of case is likely to be and suggests an alternative approach, a legal j "presumption that an adequate warning would have been^read". 480 S.W.2d at \ 606. See Restatement (Second) of.j Torts, § 402A, comment j. As the court explained: \ N Such a presumption works in favor / of the manufacturer when^an ade- j quate warning is present. Where j there is no warning, as in this case, j however, the presumption that the j user would have read an adequate / warning works in favor of the plain- f tiff user. In other words, the pre- j sumption is that Jacobs would have} read an adequate warning. The pre-1 sumption, may, however, be rebutted j if the manufacturer comes forward! with contrary evidence that the presumed fact did not exist. 480 S.W.2d at 606.

Read together, Hoover and Technical Chemical suggest a test for cases such as the one now before the Court: Where a consumer, whose injury the manufacturer should have reasonably foreseen, is injured by a product sold without a required warning, a rebuttable presumption will arise that the consumer would have read any warning provided by the manufacturer, and acted so as to minimize the risks. In the absence of evidence rebutting the presumption, a jury finding that the defendant's product was the producing cause of the plaintiff's injury would be sufficient to hold him liable.

Such a test makes sense in this case. i The jury found that the defendant's po-! lio vaccine caused Anita Reyes's polio. | ; Testimony by her mother as to what she would have done, had proper warnings been provided, would have been both speculative and self-serving. Thus we turn to the Technical Chemical presumption that a warning, had it been given,

would have been heeded. Buttressing the presumption that Mrs. Reyes might have taken preventive steps is the testimony of Reyes' expert, Dr. Ramiro Casson, that some pediatricians in Hidalgo County, at least by the time of trial, had begun administering killed-virus vaccine to infants in order to build up their level of antibodies before feeding them the live-virus drug. Tending to rebut the presumption that Mrs. Reyes would have behaved differently had she been warned was the fact that she twice returned to the Mission Clinic for further doses of vaccine, even after Anita contracted polio. Yet it is patent from her testimony that Mrs. Reyes had not, even then, been informed of the danger of the polio vaccine, and did not in fact understand what medication Anita was to receive. ^{Footnote 30}

The legal presumption suggested by the Technical Chemical opinion thus operates here to provide the final element necessary to hold Wyeth Laboratories liable for Anita Reyes' poliomyelitis. Aware of its unavoidable dangers and cognizant that it foreseeably would not be dispensed as a prescription drug, Wyeth nonetheless failed to warn Mrs. Reyes that its vaccine could cause polio in some few of the millions receiving the medication. Administered without a warning, the vaccine was "defective", hence unreasonably dangerous. According to the test we have distilled above, we must assume in the absence of evidence to the contrary that Anita's parents would have acted on the warning, had it been given. Perhaps this would have prevented her polio. It unquestionably would have avoided Wyeth's liability.

III. Having concluded that Wyeth was properly held liable under substantive law, we turn to procedural matters, specifically to Wyeth's objections to the admission or exclusion of various testimony and exhibits, and to its assertion that the evidence was insufficient to support the verdict for the plaintiffs, a) The Impeachment of Dr. Fox Among the medical experts called to testify in Wyeth's behalf was Dr. John D. Fox, Associate Dean and Professor of Epidemiology at the University of Washington School of Public Health. On cross-examination, after Dr. Fox had testified that Type III polio vaccine was less stable than either Type I or Type II, counsel for the plaintiffs attempted to impeach his testimony by reference to an uncertified transcript of an earlier trial in which Dr. Fox had been called as a witness in Wyeth's behalf. There Dr. Fox had testified that Type I polio vaccine was "unstable", with reference to its "antigenic character", and Reyes's counsel attempted to show that this earlier testimony contradicted Dr. Fox's testimony as to Type I's stability here. Upon further inquiry, however, Dr. Fox was apparently successful in explaining that his previous statement as to Type ŠI's instability dealt only with its "antigenic instability," that is, its tendency to become an "unvaccine-like" strain, whereas his comments on the instability of the Type III virus related to its propensity to cause polio in monkeys or man. On appeal, Wyeth contends that this line of questioning was improper and requires reversal, both because the testimony of an expert cannot be impeached through the use of prior incon-

sistent statements and because no proper foundation was laid.

We concur in Wyeth's conclusion that the law of Texas governs the conduct of this type of impeachment. See Wright, Law of Federal Courts, § 94 at 412-15. ^{Footnote 31}

We cannot, however, read the cases cited by the appellant as prohibiting cross-examination of expert witnesses through the use of prior inconsistent testimony. Texas does not bar impeachment of a lay witness through the use of testimony given by him at a former trial. ^{Footnote 32}

It is difficult to understand why this impeachment technique ought not be available when the witness is an expert rather than a layman. Indeed, it might be argued that prior inconsistency is a particularly appropriate weapon for attacking expert testimony, since demonstration of the inconsistency is designed not to show that the expert has erred, but that he is capable of error. See Cirilo v. Cook Paint and Varnish Co., Tex. Civ.App.1972, 476 S.W.2d 742, 748, writ ref. n. r. e. Not surprisingly, then, Texas courts endorse far-ranging cross-examination generally, and have permitted particularly wide latitude in the interrogation of an adversary's expert. See Davidson v. County of Harris, Tex.Civ. App.1970, 454 S.W.2d 830, 832, writ ref. n. r. e. Thus in Hutson v. State, Tex. Cr.App.1956, 164 Tex.Cr.R. 24, 296 S. W.2d 245, 247-248, the prosecution was permitted to impeach the testimony of a county sheriff as to the defendant's intoxication, by introducing a tape recording (made shortly after the defendant's arrest) in which the sheriff voiced an opinion contrary to that offered at trial. Also permitted in cross-examination of real estate experts has been reference to earlier inconsistent appraisals of land, the value of which is in issue. ^{Footnote 33}

A similar standard should apply to expert medical testimony. Wyeth concedes that a cross-examiner may properly inquire whether a medical expert has previously testified on behalf of the party for whom he offers testimony. But, Wyeth urges, any further foray into prior testimonial assertions is forbidden by Texas law. We do not so read the Texas cases. To be sure, no inquiry into the correctness of opinions expressed at earlier trials is proper ; ^{Footnote 34} but an inconsistency, if there is one, may be demonstrated. As we noted earlier, the purpose of such impeachment is not to demonstrate that the expert has erred, but that he is capable of error. An expert in medicine is not exempt from the use of prior testimony to prove his fallibility.

Wyeth also urges that even if permitting the impeachment was proper, counsel for Reyes failed to lay the proper foundation for the impeachment and