A serological survey of measles vaccine in a rural region of Eskişehir in Turkey

Abstract

We designed this longitudinal study as a response to measles outbreaks which occur occasionally in Eskişehir in Turkey to investigate the incidence of primary and secondary vaccine failure. The investigation was conducted over two periods (December 1993 to October 1994 and April 1995 to October 1995). Two study groups were involved, infants aged 9–11 months and children aged 18 months to 9 y. During December 1993 to October 1994 prevaccination sera was collected from 35 infants aged 9–11 months and tested to determine if maternally derived antibodies were present. The infants were vaccinated and subsequently the 31 infants who could be traced were retested 30–40 d later to determine their response to vaccination. The following was done to determine whether seropositivity rates alter over time. The second group, a randomised sample of 117 children aged between 18 months to 9 y was chosen; all of whom had been previously vaccinated and who had no history of measles. Sera was taken and tested during December 1993 to October 1994 in order to determine whether seropositivity rates varied with time. During April 1995 to October 1995 out of all the children in both groups 123 children were retested. All sera samples were studied by an enzyme-lined immunosorbent assay (ELISA). Out of the 35 infants in group 1 only four (11.4%) had maternal antibody against measles on initial testing. Out of 31 infants followed up 30–40 d after vaccination (61.3%) were found to be seropositive for measles. In the second group, of the 117 previously vaccinated children ninety-three (71.5%) had measles IgG antibody. Seropositivity rates did not show significant difference with time after vaccination. There was no association between first and second screening seropositivity rates. We conclude that the presence of maternal antibody reduces the success of vaccination. These results suggest the vaccination policy in Turkey should be re-examined with a view to revision.