Measles outbreak due to low vaccine efficacy and coverage, Mewat, Haryana, India 2015

Background: Southeast Asian Region aims to eliminate measles by 2020 but India has challenges with over 700 outbreaks and 26,333 cases in 2014. We investigated 11 measles cases in Madapur and Padheni villages that reported high vaccination coverage to identify risk factors and recommend control measures.

Methods: We defined a case as rapid onset of fever and rash with cough, coryza or conjunctivitis in a Madapur or Padheni resident between January 1 and March 28, 2015. We searched house-to-house for cases and conducted a 1:2 case control study enrolling healthy neighbors as controls. We interviewed study participants on risk factors and vaccination status and calculated vaccine efficacy. Because villages were 20 kilometers apart with no clear epidemiological link, we analysed each separately. Blood samples were tested for measles antibodies.

Results: In Madapur, population 1638, we identified 14 cases (attack rate = 1%) with median age of 2 years (range 0.2-5 years). In Padheni, population 3331, we identified 11 cases (attack rate < 1%) with median age of 4 years (range 1-8 years). No deaths due to measles in both villages. In Madapur, 39% (5/13) of cases and 82% (9/11) in Padheni were vaccinated with single dose of measles-containing vaccine. Both villages had low vaccine efficacy (48% in Padheni, 20% in Madapur). There was significant association with contact with a measles case in Padheni (Odds Ratio [OR] = 7.0, 95% Confidence Interval [CI] = 1.6-35.4) and Madapur (OR=26.2, CI = 3.6-660]. Among blood samples, 3/5 from Madapur and 9/9 from Padheni tested positive for measles-specific IgM antibodies.

Conclusion: Poor vaccine efficacy and low vaccination coverage contributed to this outbreak. We recommend improving vaccine quality and coverage to prevent future outbreaks.