Evaluation of primary failure of new measles vaccine and secondary failure of previous measles vaccine after mass vaccination in military cadets in Iran

Measles is an acute highly infectious respiratory viral disease. It remains a leading cause of death among young children especially in developing country. Measles outbreaks occurred in Iran in recent years and soldiers and cadets have been vaccinated against it. This study was designed to evaluate primary and secondary failure of measles vaccine in cadets after mass measles vaccination. For this cross-sectional study, one month after mass vaccination in 2003, all vaccinated cadets were recruited. Eight hundred and sixty five cadets were evaluated in a simple random fashion. From each individual 5ml blood sample was obtained and checked in immunology laboratory of Baqiyatallah hospital. Antibody was checked by enzyme-linked immunosorbent assay (ELISA) for qualitative and quantitative measurement of IgG and IgM in accordance with Behring ELISA kit (Germany) instructions. Cut-off OD upper than 0.2 was considered positive and quantitative titer upper than 345 mIU/ml was considered protective. All cadets were men with a mean age of 19.0±1.1 years. IgM anti-measles antibody was positive in 0.7%. Primary failure was positive in 1.8% of individuals. Anti measles IgG antibody was positive in 97.8% of cadets. History of childhood vaccination for measles was positive in 67.7% and past history of measles was positive in 23 cases (2.6%). Our results showed that secondary failure is more than 97%. Therefore, periodic studies should be performed to assess secondary failure rate in order to take preventive measures in time, of course, if its outbreaks are probable to happen.