Overall effects of immunization campaigns on child health

Introduction

The world has experienced a major decline in child mortality of more than 50% in low-income countries in the last 2-3 decades. In Guinea-Bissau, in the period 2002-2014, the Bandim Health Project (BHP) has found a 25% (95% confidence interval: 15-33%) reduction in all-cause child mortality after Oral Polio Vaccine campaigns (C-OPV) among children below 3 years of age and that C-OPV had a far better effect than other campaigns (1). Studies from Burkina Faso and Ghana have also shown reduced child mortality after C-OPV (2,3). The results from Bandim have been confirmed in data from Chakaria, Bangladesh, with a reduction in mortality rate of 32% (10-49%); again the effect of C-OPV was much stronger than the effects of other campaigns (4). Since there has been no polio infection in Guinea-Bissau, Ghana and Burkina Faso, and very little in Bangladesh, these studies strongly suggest beneficial non-specific effects of OPV. In the most recent study from the Navrongo HDSS in Ghana, we found a limited effect of C-OPV with a 4% (-5 to 12%) reduction in all-cause child mortality. However the limited effect was through triangulation of the data with previous data sets found likely to do be explained by data being from a different historical period and higher frequency of OPV campaigns conducted in Ghana (5).
References

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2.      Schoeps A, Nebié E, Fisker AB, Sié A, Zakane A; Müller O, Aaby P, Becher H. No effect of an additional early dose of measles vaccine on hospitalization or mortality in children: a randomized controlled trial. Vaccine 2018, 36: 1965-71

3.      Welaga P, Oduro A, Debpuur C, Aaby P, Ravn H, Andersen A, Binka F, Hodgson A. Fewer out-of-sequence vaccinations and reduction of child mortality in Northern Ghana. Vaccine 2017 Apr 25;35(18):2496-2503

4.      Nielsen S, Khalek MA, Benn CS, Aaby P, Hanifi SMA. National immunisation campaigns with oral polio vaccine may reduce all-cause mortality: Analysis of 2004-2019 demographic surveillance data in rural Bangladesh. EClinicalMedicine. 2021 May 24;36:100886. doi: 10.1016/j.eclinm.2021.100886. PMID: 34041458; PMCID: PMC8144662.

5.      Welaga P, Mutua MK, Ahmed Hanifi SM, Ansah P, Aaby P, Nielsen S. Effect of national immunisation campaigns with oral polio vaccine on all-cause mortality in children in rural northern Ghana: 20 years of demographic surveillance cohort data. EClinicalMedicine. 2023 Dec 5;66:102322. doi: 10.1016/j.eclinm.2023.102322. PMID: 38143803; PMCID: PMC10746391.