Target intervention to increase measles vaccination coverage by identifying low-coverage areas using Lot Quality Assurance Sampling, Chennai, India, 2012

Author (s): 

Tony Fredrick, Manoj Murhekar, Manickam P, Yuvaraj J

Background: Chennai in India reported >95% measles vaccination coverage. However, sporadic cases and outbreaks of measles were reported during 2009-11. There is considerable heterogeneity in reported coverage. In this context we surveyed one administrative area in Chennai, to estimate the measles vaccination coverage in children aged 12–23 months, identify health posts with <85% coverage and ascertain reasons for the same. Methods: We used Lot Quality Assurance Sampling to identify health posts with low-coverage. We defined lot, as an area served by a health post (i.e. ten lots). We used Lemeshow and Taber sampling plans to determine the vaccination status of 37 children aged 12–23 months in each health post, with 5% significance level and decision value of two. If more than two non-vaccinated children were identified, we considered the coverage was low (i.e. <85%), and accepted the null hypothesis. If two or less than two non-vaccinated children were identified, we considered the coverage was adequate (i.e., &#8805;85%), and rejected the null hypothesis. We pooled the data in a stratified sample to estimate overall coverage and vaccine spacing. Results: In four of the10 health posts, more than two children were not-vaccinated (i.e., coverage <85%). Overall coverage of first dose measles vaccination coverage was 92% (95%-CI = 89–94). Six percent had delayed vaccination (95% CI = 4–9) and 27% (95% CI = 23–33) received second dose. Median spacing between multidose vaccines was >35 days .Inadequate vaccination coverage was due to vaccine spacing and non-vaccination of migrant children. Conclusions: We identified areas with inadequate measles vaccination and recommended (1) targeted intervention with resource allocation (2) re-orientation of health workers to vaccinate migrant children and reduce vaccine spacing. Key Words: Measles Vaccination, low-coverage pockets identification, LQAS

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