Each year, hundreds of thousands of people are sickened from diseases from which they could have been protected if they had been vaccinated. In some low-income countries, less than half of children receive even the most widely-distributed vaccines, like the one for diphtheria, tetanus, and pertussis. So what strategies are effective at raising vaccination rates in low- and middle-income countries?

Immunizations are on our minds because of COVID-19, for which we are all hopeful there will one day be a vaccine. While that day is not imminent — many experts think the oft-cited timeline of 12-18 months estimate is optimistic— it may be useful to start thinking about what interventions will be useful once it arrives.

Education campaigns by community health workers, conducted outside of medical facilities, have shown evidence of being effective in two separate studies in Pakistan. In that context, the vast majority of children were immunized after these interventions, whereas nearly half of the children in the control groups did not receive the vaccines. Which contexts these approaches work in is still under study, and we may have some more detailed answers early next year — more on that below.

In one of the interventions, health facilitators led structured discussions separately with male and female groups of community members. Topics discussed at the meetings included the benefits of vaccinations, the costs of medical treatment for the unvaccinated, and specific community hurdles to vaccination. In the other intervention, mothers of young infants were visited in their households by trained community health workers, who presented information about vaccines with the help of pictorial information cards.

Other promising approaches include education campaigns based at health facilities, home visits, and integration of immunizations with other health services. The evidence regarding all of these types of interventions is of low certainty, however, meaning that additional research may well change our views on what is effective.

We are likely to have a better idea of what the evidence says about improving immunization rates before we have a COVID-19 vaccine. The evidence cited above was compiled in a systematic review published in 2016. Systematic reviews draw together the results from studies implemented around the world, providing stronger evidence than relying on a single case, where idiosyncratic issues can affect program outcomes. This particular review includes 14 studies across eight different types of interventions.

Here at 3ie, we're currently working on an updated systematic review on interventions to improve vaccination rates, which will draw in data from a wider set of research. For example, the new review will include studies on seven interventions with community engagement campaigns, instead of just the two cited above. We hope to publish the new review early next year.

Another question is the degree to which existing research, conducted outside of the context of a global pandemic, is still informative for planning responses during this very unusual time. For example, how can community-based strategies be implemented while social distancing restrictions are in place? Is it possible that digital approaches via social media would be able to replicate some of the benefits of community-based interventions? While this type of question is difficult to answer systematically, we're working on pulling together some evidence from other crises. Check back to blogs in this campaign in the coming weeks to see what we find.

For more information, the full systematic review from 2016 and 3ie's quality assessment of it are available here. More information on 3ie's work with vaccination campaigns is here. Beyond this study, hundreds of other systematic reviews and thousands of impact evaluations are available in our Development Evidence Portal.

This blog is part of our campaign 2020 Hindsight: What works in Development. Learn more about the campaign and read past blogs here.