Immunity to intranasal challenge with Rubella virus two years after vaccination: comparison of three vaccines.

The persistence of antibodies was studied in 143 women two years after postpartum rubella vaccination. In addition, the effect of intranasal revaccination with the RA 27/3 strain was studied in 99 women after two years. All women had responded to primary immunization with the development of hemagglutination-inhibiting antibodies. Intranasal revaccination resulted in a significant rise in titer of hemagglutination-inhibiting antibodies in 9% of the vaccinees who received the RA 27/3 strain compared with 53% and 24% of those who received the Cendehill and HPV-77 DE-5 vaccines, respectively. The difference between the response in the RA 27/3 group and that in the C Cendehill group was statistically significant (P less than 0.001), as was the difference between the response of the latter group and that of the HPV-77 DE-5 group (0.03 greater than P greater than 0.01). The susceptibility to intranasal challenge was found to be related to low levels of serum hemagglutination-inhibiting antibodies. The titers of hemagglutination-inhibiting antibody were well maintained during the follow-up period, but three of the 52 Cendehill vaccinees had titers of less than 1:10 after two years.