| Abstract: | In the serological survey of 2009 children immunized against measles 285 children (14.2%) were found to be seronegative to this infection in the hemagglutination inhibition test with 4 hemagglutinating units of the antigen. Among 1724 immunized children showing positive response to vaccination and placed under dynamic observation for 11 years, 2 cases of measles were registered. At the same time, in the dynamic observation of 111 seronegative children 66 measles cases (59.5%) were registered during the above period, while among 169 children, also seronegative, but receiving booster immunization against measles, morbidity rate was only 1.2%. In some vaccinees the decrease of postvaccinal immunity to seronegative values was observed, but such decrease had no essential influence on the morbidity level among the vaccines. The increase of measles morbidity among schoolchildren immunized against this infection was due not to the decrease of their postvaccinal immunity, but to their concentration in schools and to their more intensive contacts with the sources of infection in comparison with children of preschool age. |
