Rubella viraemia and antibody responses after rubella vaccination and reimmunization.

Eleven 4-13 year old schoolgirls, who were seronegative by haemagglutination inhibition (HI) and radioimmunoassay (RIA) tests despite having been given HPV77-DE5 vaccine 3-9 years previously, were revaccinated with RA27/3. They showed evidence of residual immunity since they had accelerated immune responses, little or no rubella-specific IgM, no viraemia, and no vaccine-induced reactions. In contrast, all but one of the five adult women who were primary vaccinees showed a more delayed immune response. Three of four women tested had viraemia and two had vaccine-induced reactions. Enhanced HI and enhanced RIA showed that many of the schoolgirls had antibody before challenge, as did a fifth adult, who also showed an accelerated immune response, yet became viraemic.

Rubella, measles and mumps antibodies following vaccination of children. A potential rubella problem.

One hundred sixty-eight children immunized by one suburban Minneapolis clinic during routine pediatric visits had serum antibodies measured to determine the efficacy of rubella (HPV77 DE5 strain), measles (Edmonston B and Moraten strains), and mumps (Jeryl Lynn strain) vaccines. Serologic failure rates at the mean postvaccination times tested were as follows: rubella, 36% (4.7 years); measles, 18% (6.5 years); and mumps, 9% (4.5 years). Antibody titers shortly after vaccination were not done, so seronegative subjects may never have responded or their titers may have declined with time; our rubella data suggest the former. Children vaccinated with rubella and measles at less than 14 months of age had higher failure rates than those vaccinated at a later age. This supports postponement of rubella and measles vaccinations until at least 15 months of age. In addition to current measles reimmunization policies, consideration also should be given to reimmunizing girls who were given rubella vaccine at less than 14 months of age. Twenty-four percent (19/79) of children vaccinated with HPV77 DE5 strain rubella at 14 months or older had rubella hemagglutination-inhibiting titers less than 8. This is disturbing and, if confirmed by others, would prompt the use of a different strain of rubella vaccine for routine immunization.