Seasonal influenza vaccine policy, use and effectiveness in the tropics and subtropics – a systematic literature review

Abstract

AimThe evidence needed for tropical countries to take informed decisions on influenza vaccination is scarce. This article reviews policy, availability, use and effectiveness of seasonal influenza vaccine in tropical and subtropical countries.MethodGlobal health databases were searched in three thematic areas – policy, availability and protective benefits in the context of human seasonal influenza vaccine in the tropics and subtropics. We excluded studies on monovalent pandemic influenza vaccine, vaccine safety, immunogenicity and uptake, and disease burden.ResultsSeventy‐four countries in the tropics and subtropics representing 60% of the world's population did not have a national vaccination policy against seasonal influenza. Thirty‐eight countries used the Northern Hemisphere and 21 countries the Southern Hemisphere formulation. Forty‐six countries targeted children and 57 targeted the elderly; though, the age cut‐offs varied. Influenza vaccine supply increased twofold in recent years. However, coverage remained lower than five per 1000 population. Vaccine protection against laboratory‐confirmed influenza in the tropics ranged from 0% to 42% in the elderly, 20–77% in children and 50–59% in healthy adults. Vaccinating pregnant women against seasonal influenza prevented laboratory‐confirmed influenza in both mothers (50%) and their infants <6 months (49–63%).ConclusionGuidelines on vaccine composition, priority risk groups and vaccine availability varied widely. The evidence on vaccine protection was scarce. Countries in the tropics and subtropics need to strengthen and expand their evidence‐base required for making informed decisions on influenza vaccine introduction and expansion, and how much benefit to expect.

Year-round influenza immunisation during pregnancy in Nepal: a phase 4, randomised, placebo-controlled trial

“…A quadrivalent vaccine with both type B antigens, which is available in some countries, would probably have resulted in a greater effect. 12,14 …”

“…An estimated 40% of the world’s population live in tropical zones, yet influenza vaccines are not widely used in this setting. Despite year-round circulation 12–14 of influenza in tropical and subtropical regions, we are not aware of previous prospective or controlled randomised studies assessing year-round influenza immunisation from Asia. 15 …”

Epidemiologic and Spatiotemporal Characterization of Influenza and Severe Acute Respiratory Infection in Uganda, 2010-2015

“…Similarly, the macroeconomic impact of seasonal influenza epidemics in the labor-intensive economies of sub-Saharan Africa is estimated to be substantial, and in the context of a pandemic would likely be considerably higher than in high-income countries (18). Although vaccination remains one of the most effective pandemic mitigation and control strategies, a recent systematic review estimated influenza vaccine coverage in subSaharan Africa at ,1% (19). In Uganda, baseline influenza vaccination rates are similarly low, with ,1% of our study sample reporting a history of vaccination.…”

The WHO global influenza surveillance and response system (GISRS)—A future perspective

“…Bolstered by very active technical support in the provision of protocols and CDC diagnostic reagents for detection of seasonal and zoonotic (novel) infections, all regularly updated, and including training and associated performance evaluation, this momentum is likely to continue. Provision of guidance documents and analysis tools by GIP will continue to enhance the capabilities of laboratories to conduct epidemiological and virological surveillance and evaluate the burden of disease from influenza and how influenza might impact other diseases, essential to develop seasonal vaccination policies . A 21% increase in countries with flu vaccine policies between 2006 and 2016, complemented by an 87% increase in global vaccine distribution between 2004 and 2013 bodes well for the future.…”