Immune response to measles vaccine after mass vaccination in Urmia, Islamic Republic of Iran

We investigated the effectiveness of the mass measles vaccination campaign in Urmia, Islamic Republic of Iran, by examining the measles IgG seroprevalence and antibody response from paired data before and after the campaign. The overall seropositive rate of 624 subjects aged 5-25 years increased 1 year after the mass vaccination [from 53.0% to 72.3%]. A rise in antibody titre occurred in all age groups except the 21-25 years group, which had the highest titre before mass vaccination. On logistic regression analysis, only immune status prior to vaccination was significantly associated with the seroresponse. It may be cost-effective to check antibody titres before mass vaccinations, especially in high vaccine coverage regions with circulating wild virus

Measles IgG sero-prevalence and its attributable factors in 5-25-year-old cases prior mass vaccination campaign in Urmia, northeastern Iran

Measles is a vaccine preventable infectious disease. Despite the widespread availability of an effective measles vaccine, the number of measles cases is noticeable in Iran. Because measles -specific antibody titer after vaccination is lower than after natural infection there is a concern that vaccinated persons may gradually lose protection from measles. This study was performed to examine the persistence of vaccine-induced antibody, participants with documented history of vaccination were assessed to determine the sero-prevalence and titer of measles antibody. This study was carried out in Urmia. Iran. Documented history of at least a single dose of live attenuated measles vaccine [at 9 or 15 month of age] was the inclusion criteria. Blood was collected from 835 subjects between 5 and 25 years old. The sera were tested for anti-measles IgG antibodies, by ELISA [IBL Germany]. Associations between predictive factors such as demographic data, vaccination status [once or twice] with IgG sero prevalence in routine vaccinated subjects were investigated by logistic regression analysis. The antibody titers in 54.76% of cases were in the range of protective level [IgG>12IU]. The mean of antibody titer significantly increased after the 16th year of life. The antibody titers were higher in participants who received one dose of measles vaccine in comparison with the persons who received a booster of measles vaccine. Antibody titers were slightly higher in men than in women. On multiple logistic regression analysis, of all variables examined, only vaccination status retained a significant association with antimeasles sero-positivity rate [estimated odds ratio = 0.395 95% CI = 0.214-0.859, P<0.05]. Elevation of antibody titer many years after vaccination is most likely due to boosting effect from repeated exposure to circulating wild virus resulting in unapparent or sub-clinical re-infection. This group of persons would be the most likely to support viral transmission in the absence of disease