A general measles vaccination campaign in urban Guinea-Bissau: Comparing child mortality among participants and non-participants

Highlights

• Measles vaccination campaigns may reduce child mortality substantially.

• The reductions were greatest among girls and children already measles vaccinated.

• Measles vaccination campaigns may have non-specific effects.

Abstract

Background

Measles vaccination campaigns targeting children aged 9–59 months are conducted every three years in Guinea-Bissau. Studies have demonstrated beneficial non-specific effects of measles vaccine. We compared mortality one year after the December 2012 measles vaccination campaign in Bissau city for children who received campaign measles vaccine with children who did not receive campaign measles vaccine.

Methods

Field workers from Bandim Health Project registered all children living in the Bandim Health Project’s study area who received measles vaccination at the campaign posts. Children not seen during the campaign were visited at home and campaign participation status was assessed. We compared mortality rates of participants vs. non-participants in Cox regression models.

Results

5633 children aged 9–59 months (85%) received campaign measles vaccination and 1006 (15%) did not. During the subsequent year 16 children died. Adjusted for background factors, the hazard ratio (HR) comparing measles vaccinated versus unvaccinated was 0.28 (95% CI: 0.10–0.77). The benefit was larger for girls (HR: 0.17 (0.05–0.59)) and for children who had received routine measles vaccine before the campaign (HR: 0.15 (0.04–0.63)).

Conclusions

We found indications of strong beneficial non-specific effects of receiving measles vaccine during the 2012 campaign, especially for girls and children with previous routine measles vaccination. Measles vaccination campaigns may be an effective way of improving child survival.

Introduction

A second dose of measles vaccine is recommended to control measles infection. WHO recommends integrating the second dose in the routine vaccination programme in countries where coverage of the first measles vaccine dose exceeds 80% for three consecutive years [1]. In countries where this has not been reached, administration of the second measles vaccine dose is recommended through measles vaccination campaigns or supplementary immunization activities (SIAs) [1]. SIAs aim to reach children who missed out on the routine services and/or who did not seroconvert after the first dose [1]. From 2001 to 2011 SIAs were conducted with regular intervals in more than 80 high measles burden countries [2].

The national estimated coverage rates for the first dose of measles vaccine in Guinea-Bissau was 69% between 2009 and 2012 [3]. Thus, since 2006, measles vaccination campaigns have been conducted every 3 years in Guinea-Bissau, targeting all children between 9 months and 5 years of age regardless of vaccination history [4].

Apart from conferring immunity against measles infection and measles related morbidity and mortality, measles vaccine has been associated with marked reductions in childhood mortality beyond what can be explained by prevention of measles infection. Thus, measles vaccine was associated with reductions in child mortality of almost 50% in a recent WHO commissioned review [5]. These “non-specific effects” have been observed in both randomized controlled trials [6], [7] and in observational studies [8], [9]. Furthermore, the non-specific effects associated with measles vaccination seem to be stronger for girls [6], [7], [10] and receiving two doses of measles vaccine seems to reduce mortality even more than receiving only one dose [7], [11], [12].

Measles vaccination campaigns have proven effective in reducing measles incidence and associated morbidity/mortality [13]. However, the effect of measles vaccination campaigns on overall child mortality has only been assessed in one previous study from rural Guinea-Bissau, where all-cause child mortality in the year following the 2006 measles vaccination campaign was 20% lower compared with the two previous years. The effects of campaign measles vaccination tended to be stronger in girls and among children who had previously received routine measles vaccination [12].

In December 2012, a national campaign with measles vaccination, Vitamin A supplementation and deworming (mebendazole) took place in Guinea-Bissau. We compared all-cause mortality in the year after the campaign for children who received campaign measles vaccination and children who did not receive campaign measles vaccination.