Impact of Measles Vaccination on the Acquisition and Frequency of Measles Infection in Province of Sindh

Objective: To determine the status of vaccination among confirmed measles cases and to determine the association of vaccination status with the occurrence of measles infection. Methods: A cross-sectional survey was carried out in the province of Sindh from January 2016 to April 2016. The study included patients of both gender, 9 months of age, fulfilling the case definition of measles by World Health Organization (WHO), who were reported to and/or picked by the measles surveillance officers. A sample of 3-5 ml of blood was collected from each registered patient between day 4 and day 28 of the rash to test for measles IgM antibodies. The samples were labelled and sent to National Measles Laboratory, National Institute of Health (NIH) Islamabad in reverse cold chain. Patients who tested positive for IgM antibodies were grouped as confirmed measles while patients negative for measles IgM antibodies were grouped as suspected measles. Data of both the groups was analysed using windows SPSS 21 for vaccination status, for frequency of measles infection against the number of doses of measles vaccine received. Frequencies of vaccination among confirmed measles cases were compared with suspected measles for statistical significance using Chi-square. P-value of <0.05 was taken as significant. Results: A total of 572 out of 915 study subjects were confirmed measles cases, of which 258 (45%)were never vaccinated against the disease as compared to 72 (12.6%) who were completely vaccinated. Overall, 128 (37.3%) were fully vaccinated amongst suspected measles. Vaccination status was not known in a quarter of patients in both groups. A significant association was found between the vaccination status and measles infection with higher frequency of measles in unvaccinated as compared to the vaccinated (p<0.001). Conclusion: We conclude that the vaccination rate among measles patients was significantly lower than among non-measles patients. A sizable 12.6% got the disease in spite of completing measles vaccination.