Postinfection and postvaccination antirubella immunity

Out of 1670 pregnant women contacts examined for antibodies to rubella virus, recent rubella infection was confirmed in 5.1% of subjects, 2.2% of which were symptomatic and 2.9% asymptomatic; 89.9% of tested women were seropositive. These results closely resembled those, obtained in serological surveys, carried out in Poland several times in the years 1969-82. Rubella antibodies were found in over 90% of women in childbearing age, with HI antibody geometric mean titre (GMT) 58.7-84.3 (depending on the epidemiologic situation). Especially high GMT--of 122--was detected in women of the 30-34 year age group after the rubella epidemic in 1980/81, which showed the highest rubella morbidity of 5-9 year-old children. Reactogenicity and immune response in 10-13 year-old vaccinated girls were investigated. Seroconversion among seronegatives, among subjects with low antibody level (less than 1:20) and among seropositives with antibody titres 40 or higher before vaccination occurred in 99.8%, 60% and 12.8% of cases, respectively. HI antibody GMT after immunization was 132.6-135, similar to GMT induced by naturally acquired infection in the women of 30-34 year age group after the rubella epidemic. The difference of GMT in vaccinated girls with joint symptoms (152) and without postvaccinal reactions (124) was statistically significant. Practical conclusions for rubella diagnostic and vaccination programmes based on the analogies and differences of antirubella immunity in infected pregnant women, in naturally infected children and adults, and in vaccinated subjects are discussed.