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

In spite of vaccination, outbreaks of measles occur in many countries, and measles remains the most frequent cause of death among vaccine preventable diseases.. 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 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.. 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 non-revaccinated 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 non-revaccinated 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).. 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