Rubella seroconversion following immunization in a rural practice

One hundred two consecutive patients with verifiable immunization to rubella were studied in a rural West Virginia county. Hemagglutination Inhibiting (HI) antibody titres, age at immunization, and elapsed time since immunization were recorded. Twenty-three (22.5 percent) had HI titres less than 1:8. There was no statistically significant difference in whether immunization at less than 15 months or more than 15 months of age resulted in a titre of greater than or equal to 1:8. There was no evident change in group proportion of seroconversion with time; either the child initially had a seroconversion with immunization, or he/she did not. A relatively large number of children with verified immunization to rubella do not have a titre currently considered protective to rubella. This does not seem to vary with time since immunization or age at immunization.