Adult vaccination uptake strategies in low- and middle-income countries: A systematic review.

BACKGROUND

Evidence-based strategies can maximize vaccination intent and uptake among adults. This systematic review summarizes the existing literature on strategies to improve vaccination intent and uptake among adults in low- and middle-income countries (LMICs) to inform future implementation in various populations and contexts.

METHODS

Eligible studies were identified through a systematic search in Medline, Embase, Cochrane Libraries, as well as grey literature databases published between January 2010 and March 2021. The search was limited to studies in LMICs that evaluated adult vaccination interventions. Data were extracted from the included studies and evaluated against the World Health Organization's Behavioral and Social Drivers of Vaccination Framework. The National Institutes of Health study quality assessment tools were used to evaluate study quality.

RESULTS

The initial literature review identified 2,854 records, 22 of which met the inclusion criteria. The majority (n = 19 or 86%) of studies were from middle-income countries, with the remaining studies (n = 3 or 13%) set in low-income countries. The majority (15/22, 68%) of interventions were multi-component. 82% (18/22) of studies addressed thoughts and feelings, 59% (13/22) addressed social processes, and 73% (16/22) addressed practical issues. Five studies reported primary outcomes of vaccination intent, and the remaining 17 reported vaccine uptake. 36% (8/22) of the studies cited statistically significant positive intervention effects on vaccination intent or uptake. Few of the included studies (6/22, 27%) were RTCs, and most studies (15/22, 68%) were of poor study quality. The studies reporting the highest increase in vaccination intent and uptake were multi-component interventions that addressed all three determinants of vaccination.

DISCUSSION

The results of this review highlight levers that can be used to encourage vaccine intent and uptake in the ongoing rollout of COVID-19 vaccines, as well as the deployment of other vaccines to adult populations in LMICs. Of the included studies, multicomponent interventions were most effective, mainly when targeting multiple determinants of vaccination. However, poor study quality indicates the need for additional research to validate these findings.