Serological Response to Measles Revaccination in a Small Population After a Mass Measles Revaccination Program

Background: in spite of vaccination, outbreaks of measles occur in many countries, and measles remains the most frequent cause of death among vaccine preventable diseases. objectives: to compare anti-measles antibody titer between revaccinated and non-revaccinated medical students 2 years after the national mr (measles, rubella) vaccination program, which was implemented in 2002-2003 for individuals aged 5 to 25 years in iran. patients and methods: this stratified cross-sectional study was conducted on 78 revaccinated and unvaccinated for national mmr vaccination (2002) medical students aged 22-25 years, who attended our markaz tebi children hospital in tehran for their pediatric rotation from summer to winter in 2005. the revaccinated group was selected by simple random sampling from a list of names of the students and the non-revaccinated group included all the non-revaccinated students. serum igg and igm anti-measles antibody titers of the subjects were measured using indirect enzyme-linked immunosorbent assay (elisa), and the levels were compared between the 2 groups of students. data were analyzed using chi square test and independent samples t test. statistical significance was defined as p values of < 0.05 by spss ver.13 software. results: overall, we recruited 45 subjects with a mean age of 23.7 ± 0.12 years in the revaccinated group and 33 subjects with a mean age of 24 ± 0.25 years in the non-revaccinated group (p = 0.2). the mean anti-measles igg antibody titer was 31.8 ± 21.2 iu/ml (range, 1-190 iu/ml) in the revaccinated group and 6.12 ± 8.8 iu/ml (range, 1-45 iu/ml) in the nonrevaccinated group (p < 0.001). the mean anti-measles igm antibody titers were 2.6 ± 6.7 iu/ml (range, 1-45 iu/ml) and 1 ± 0 iu/ml (range, 0-1 iu/ml) in the revaccinated and nonrevaccinated groups, respectively (p = 0.1). anti-measles igg was present (serum titer ≥ 13 iu/ml) in 46.7% of the individuals of the revaccinated group and 6% of the individuals of the non-revaccinated group (p < 0.001). conclusions: the results of this study indicate that although the percentage of individuals with protective levels of anti-measles antibody increased to 46.7% after revaccination, the protection was inadequate in more than 50% of vaccine recipients, thereby, emphasizing the need for checking antibody levels after revaccination.