A man covers his face in fear while receiving a vaccine from a nurse wearing a face mask

Many people are reluctant to get vaccinations, often owing to a fear of needles or misinformation about the jabs.Credit: Genaro Molina/Los Angeles Times/Getty

Vaccines save lives. The measles vaccine alone is estimated to have averted 23 million deaths between 2000 and 2018, according to the World Health Organization (WHO). Data from a subset of countries where girls are vaccinated against the human papillomavirus show that precancerous cervical lesions in girls aged 15–19 plummeted by 51% within a few years of vaccine rollout1. Globally, vaccination rates are increasing for many diseases. However, in 2022 (the latest year for which data are available), there were still 14.3 million ‘zero-dose’ children — those who had not received any routine immunizations.

A lack of access to vaccines and the high costs of producing and purchasing them are among the main reasons for low uptake, especially in low- and middle-income countries. In high-income countries, vaccine hesitancy is a significant factor2. This is fuelled, in part, by misinformation, which is a problem worldwide3.

Countries already have a range of strategies for boosting uptake. All should study the work of researchers who have been evaluating the effectiveness of different interventions. The burgeoning science of vaccine-uptake effectiveness is throwing up some unexpected results that could help public-health authorities to sharpen their policies — and save more lives.

Take the United States. By October 2022, almost two years after the first COVID-19 vaccines were rolled out, 80% of people in the country aged six months and older had received at least one dose. However, only 33% had received a follow-up booster, which offers the highest possible level of protection against the SARS-CoV-2 virus.

The low booster numbers drove some states to investigate how uptake might be increased. Researchers and health authorities have highlighted ‘last-mile vaccination delivery’ as a major barrier to uptake. In 2021, the White House came up with the idea of encouraging people to get their boosters by offering them free transport to clinics through the ride-hailing companies Lyft and Uber. But a study published in Nature last month4 shows that this might have done little to increase booster uptake.

Economist Katherine Milkman at the University of Pennsylvania (UPenn) in Philadelphia and her colleagues compared the offer of a free ride with other interventions in a study involving 3.66 million patients of CVS Pharmacy, a retailer that provides vaccination services. The patients, who had all previously been vaccinated against COVID-19, were split into eight groups. One group received a text message offering free transport to the pharmacy; the other seven were sent different text-message reminders to get their boosters.

People offered free transport were not more likely to get vaccinated than were those who received the other kinds of text message. Messages that had a more positive effect included one proposing an appointment for a day of the week and time of day similar to that of a patient’s previous vaccination, and one informing the recipient that infection rates were high in their county.

“Our article really highlights the importance of testing policy,” says study co-author Sean Ellis, also at UPenn. “Whatever policy we’re putting into place, we should be robustly evaluating whether it actually works, so that if it does work, we can scale it up or continue to do it. And if it doesn’t, we can move on from it and try something else.” In other words, studies are needed to evaluate whether ‘common sense’ interventions actually work in practice.

Researchers are also helping to evaluate the overall effectiveness of text messaging on vaccine uptake. In a study published in May, Hongyu Guan at Shaanxi Normal University in Xi’an, China, and colleagues used the 2021 Chinese General Social Survey, a periodic national survey of households, to examine the actions of 7,281 people. They found that those who received notifications from their local government or community residents’ committees advising them to get vaccinated were twice as likely to get a COVID-19 vaccine than were those who did not5.

The same study showed that the practice also increased influenza vaccine uptake, albeit from a much lower base. Uptake was more than 40% higher for those notified compared with those who did not receive a text message. This finding builds on the work of earlier studies6. However, researchers are less certain whether these approaches are effective for people who are reluctant to be vaccinated7.

In low-income countries, research shows that uptake increases when vaccines are taken into communities. In Sierra Leone, for example, the average person lives 3.5 hours away from a vaccination centre and the cost to travel there exceeds their weekly wage. A study published in March8 found that significantly more people in the country received their COVID-19 vaccines when mobile teams of vaccinators were deployed to 150 rural communities.

Increasing vaccine access and accessibility saves lives, but is only part of the equation. Other interventions are needed to maximize uptake, and these must undergo rigorous testing in different regions and contexts to help health authorities to determine what works. The obvious answer is not always the right one, and the vagaries of human behaviour can thwart seemingly logical solutions.

Source link