Measurement of Serum Antibody Titer against Measles in a group of Adults Receiving Measles-Rubella Mass Vaccination

Background: Measles vaccination in Iran is an expanded program. Since 1973- 2002, all infants have received live attenuated measles vaccine (0.5 ml, subcutaneous, A.I.K strain) at the 9th and 15th months of life. Before 2002, we confronted outbreaks of measles in previously vaccinated adults from all over the country. Reports showed convincing evidence of secondary measles vaccine failure. The Ministry of Health and Medical Sciences of the Islamic Republic of Iran launched a mass Measles-Rubella (MR) vaccination campaign throughout the country from 5 to 31 December 2003. More than 32 million inhabitants between 5 and 25 years old received the Measles-Rubella (MR) vaccine. The aim of this program was to eliminate measles and to control congenital rubella syndrome. This study was conducted to determine the prevalence of positive measles antibody titers in a group of adults who received mass MR vaccine.Methods: We conducted this cross-sectional survey on a group of adults 20–30 years old (30 men and 30 women) referred to marriage consulting clinic in Isfahan University of Medical Sciences in 2008. All participants had received routine vaccination against measles during their infancy and MR mass vaccination in December 2003. Serum IgG measles antibody was measured using ELISA (Trinity Biotech, Bay, Ireland). We considered immune serum Ratio (ISR), antibody titers of ≤ 0.09 IU/µl as negative, 0.91–1.09 IU/µl as intermediate, and ≥ 1.10 IU/µl as positive respectively. Data were analyzed by SSPS software Student-t and Pearson correlation tests at the significance level of P < 0.05.Finding: In women group, all had positive titers (100%); in men group, 27 (90%) positive titer, two (6.6%) borderlines, and one (3.4) negative titer were seen. The mean serum antibody titer in women was 2.02 ± 0.56 IU/µl and in men was 1.91 ± 0.53 IU/µl. The mean serum titer in 20-23 years old group was 1.84 IU/µl, in 24-27 years old was 2.12 IU/µl and in 28-30 years old was 2.17 IU/µl. No statistically significant correlation was found between serum antibody titer and age (P = 0.136). The correlation between antibody titer and sex also did not turn to be statistically significant (P = 0.447).Conclusion: In our study, 100% of women and about 96% of men had positive protective serum titer, meaning that there has been a good vaccine induced protection for the majority of vaccinates volunteers. However, for interruption of virus transmission in the community, more than 95% of the population must be protected.