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

Abstract

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, ³9 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  sta- tus was not known in a quarter of patients in  both  groups.  A  significant  association  was  found  be- tween 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.