title: The minimum protective level of antibodies in smallpox.
abstract: Blood samples from 57 contacts of 6 smallpox cases were tested for haemagglutination-inhibiting (HI) and neutralizing antibodies. All 6 contacts who subsequently developed smallpox were unvaccinated and had neutralizing antibody titres of 10 or less. However, 6 unvaccinated contacts with similar antibody levels did not develop smallpox. None of the 41 vaccinated contacts, regardless of their antibody level, contracted the disease.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007109:Immunity; D007194:India; D008297:Male; D008875:Middle Aged; D012899:Smallpox / Q000276:immunology* / Q000517:prevention & control; D014611:Vaccination
chemical_list: D000914:Antibodies, Viral