RESUMEN
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