Animal pain and distress in vaccine testing in the United States.

National statistics on animal use in research can provide guidance in setting priorities for research into alternative methods, i.e., those methods that can replace, reduce, or refine animal-based procedures. All else being equal, fields of research causing the most suffering to the largest numbers of animals should be considered prime candidates for alternative research. We examined national statistics on animal use in research in the United States to determine the extent to which vaccine testing accounts for those animals that experience unrelieved pain and distress. During 1998, 96,536 regulated animals were reported to have experienced unrelieved pain and distress in research (laboratory-bred mice and rats, as well as all non-mammals, are excluded from the U.S. reporting system). Vaccine-related testing alone accounted for 61% of this total. Of the 58,820 animals used in such vaccine testing, nearly all were hamsters (68%) and guinea pigs (28%), at least 74% were used in potency tests, and at least 55% were used in testing of Leptospira vaccine. This analysis and an earlier one both underscore the need to develop and implement alternative methods in vaccine testing.