What we know about vaccine hesitancy

By Dylan Barry, GCPPP staff, June 10th, 2021

The cumulative number of COVID-19 vaccine doses manufactured and administered worldwide has hit two billion and the pace of vaccinations has also picked up, to more than 34 million doses a day. Nevertheless, in some of the advanced economies—where vaccination levels are highest—a new obstacle must now be overcome: the limits of vaccine demand.

In opinion surveys, the levels of reported resistance to vaccination in the majority of countries have remained high enough to pose a real threat to the odds of achieving the ‘herd immunity’ needed to suppress the virus. Fortunately, a combination of time and the mounting evidence of COVID-19 vaccines’ safety and efficacy, are reducing this resistance. The world is seeing a kind of contest between anticipatory reluctance and ultimate acceptance, and which in the advanced countries has shown acceptance rising strongly.

But will vaccine hesitancy ultimately be reduced by enough to enable the virus to be suppressed? In this analysis, we summarise the evidence on vaccine hesitancy, its causes and how it continues to evolve.

The trouble with vaccine hesitancy

The definition of vaccine hesitancy settled on by the SAGE Working Group on Vaccine Hesitancy in the UK is “the delayed acceptance or continued refusal of a vaccine despite the availability of vaccination services.”

For a population to reach herd immunity against the novel coronavirus, a condition under which the virus runs short of hosts within which to reproduce, a large majority will need to be inoculated against it. In the early days of the pandemic, the most frequently cited number was 60-70 percent of a population, but the truth is that the level varies disease-by-disease. For some highly transmissible viruses, like measles, that figure can be as much as 95 percent. The more recent consensus, recently evoked by Dr Anthony Fauci, the White House’s medical advisor, is that herd immunity against the coronavirus will probably require vaccination levels closer to that of measles—somewhere between 70 and 90 percent of a given population.

That leaves little room for hold-outs. Yet in most countries the levels of hesitancy declared in opinion polls have been well in excess of that figure. The polling outfit Gallup recently shared the results from a worldwide survey on the issue. Between October 2020 and January 2021, the company interviewed at least 1,000 respondents in each of 116 countries about their attitude toward COVID-19 vaccines (see charts).

Most of that polling took place before any COVID-19 vaccines had been approved or deployed, offering a window into countries’ baseline vaccine hesitancy levels but not into subsequent acceptance. The survey found that 68% of adult respondents worldwide said they were willing to be vaccinated if a coronavirus vaccine was made available to them at no cost. Given the sample is representative, that means that 32% of the world’s adult population may still be likely to refuse a vaccine—the equivalent of 1.3 billion people worldwide. If maintained in real decisions, that would be cause for concern.

The motivations behind vaccine hesitancy

The reasons people feel hesitant to get vaccinated against the coronavirus are often complex, but a handful of reasons dominate. In the United States, the results of the ongoing Household Pulse survey administered by the United States Census Bureau report that the most frequently given reasons for avoiding vaccination are fear about the side-effects of COVID-19 vaccines; a distrust of the vaccines themselves; and a general distrust in government. Those responses are consistent with findings from elsewhere in the world.

Those reasons are somewhat intractable. Nevertheless, they are immediately followed by “don’t believe I need it”, “plan to wait and see” and “don’t know if it will work,” leaving the door open to people changing their minds with time and evidence, although the desire to be a free-rider—to benefit from others’ immunity without being vaccinated yourself—could prove to be a persistent challenge.

Distrust in government is especially important in explaining the global distribution of vaccine hesitancy. The world’s highest rates of vaccine hesitancy are in the former Soviet Union and Eastern Bloc, where populations scarred by decades of surveillance and a brand of authoritarianism especially prone to encourage conspiracy theories are understandably distrustful of their governments. The worst case is Kazakhstan, where Gallup reports that only 25 percent of respondents would be willing to get a COVID-19 vaccine.

The same is true of countries that have a history of major government health scandals. The archetypal example is France, which has some of the highest levels of vaccine hesitancy in the developed world. For many decades, the country was overwhelmingly supportive of vaccination. Then, the revelation that France’s National Centre for Blood Transfusion had knowingly allowed HIV contaminated blood to be given to patients between 1980 and 1985 rocked the public’s confidence in its health authorities. Of France’s 3,000 known haemophiliacs, 1,200 contracted the virus—resulting in the deaths of at least 200 people.

The public’s attitude to vaccines hardened further in 1998 after the government’s handling of a reported (though spurious) link between a rise in multiple-sclerosis cases in the country and a national vaccination campaign against Hepatitis B. The campaign was ultimately suspended, despite no evidence of a link with multiple sclerosis. Finally, the French government’s response to the 2009 swine-flu pandemic, in which millions of ultimately unused vaccines were purchased at great expense, only further undermined public confidence in vaccines by making them appear unnecessary, even irrelevant.

Demographic and temporal trends in vaccine hesitancy

The distribution of vaccine hesitancy within societies is also revealing. In many countries for which data is available, vaccine hesitancy is highest in disadvantaged or minority ethnic groups. It is also higher in younger age groups than older ones and in those with less formal education. The next three charts, using data from the US Census Bureau’s Household Pulse Survey, demonstrate this clearly.

But thanks to being updated regularly the Survey and the charts also demonstrate something more encouraging: how dramatically vaccine hesitancy has shrunk across all demographics in the United States since January, when actual vaccinations commenced. In most cases, the decline is going a long way towards equalising levels of hesitancy across what were significant demographic divides and, just as importantly, showing it reducing to levels consistent with the ultimate achievement of herd immunity. At least in the US, acceptance is winning out against anticipatory reluctance.

In the United States, the elevated levels of vaccine hesitancy in the African-American community have received a lot of coverage, but the same is true of minority ethnic groups and indigenous communities in the United Kingdom, Canada, Australia and New Zealand, amongst others. Interestingly, the same is also true of South Africa’s white—but far from disadvantaged—minority, although clearly for different reasons.

In this case, distrust in government is once again an important factor. For disadvantaged minority communities, health authorities have historically often been explicitly antagonistic. The most frequently cited example is the 40-year-long Tuskegee Experiment, in which 399 African-American men in Alabama were lied to by the United States Public Health Service about being treated for syphilis, while being left for their condition to worsen.

More recent attention has focused on the story of Henrietta Lacks, an African American woman who died from cervical cancer in 1951, but whose cell cultures were used in research for decades without her or family’s consent. Nevertheless, even when health authorities are not being explicitly antagonistic, ethnic minorities often receive a worse standard of care in health institutions. It is consequently little surprise that vaccine hesitancy is higher in these communities. By the same token, however, thanks to relative poverty and to poor health care, ethnic minorities have also suffered higher mortality due to COVID-19, which may have ultimately increased the motivation to get vaccinated, once vaccines had been seen to be safe.

There is little evidence that gender is a major determinant of vaccine hesitancy, but age is a significant factor. In most countries for which data is available, vaccine hesitancy tends to be highest in the young and lowest in the elderly. There are two major explanations for this. The first is intuitive: the risk of dying from a serious case of COVID-19 is much lower among young people than amongst the elderly and so the perceived risk-reward payoff of getting vaccinated is different (although that may change with new variants.)

The second is subtler: vaccine hesitancy is strongly associated with the use of social media, disproportionately a young persons’ domain and a largely uncontrolled channel for rumour and conspiracy theories. According to research by Eurofound, an agency of the European Union, the vaccine-hesitant are much more likely to spend time on social media and to consider social media their main source of information.

Finally, education level is also a good predictor of vaccine hesitancy, at least in places like the United States and the United Kingdom. The fewer years of education a person has, the more likely they are to be vaccine hesitant. That assertion requires a caveat, however. There is a strong likelihood that this is not a causal relationship, but rather a side-effect of the particular dynamics between education, partisan politics and vaccine hesitancy in those countries. The opposite is true in South Africa, for example.

What can be done about vaccine hesitancy

Those are the outlines of the global problem of vaccine hesitancy and of its evolution in one of the countries whose vaccination programme is well advanced. What can be done to limit it? The most obvious approach is to incentivise vaccine uptake. This has been done in a variety of ways worldwide.

In Moscow, residents are wooed into getting the Sputnik V vaccine with ice cream, a strategy since adopted by Unilever. In the United States, vaccine lotteries with large cash prizes or the promise of free college tuition are proving especially powerful in swaying people on the fence. There have now been such lotteries in all of New York, California, Oregon and Ohio, with other states likely to join. Private companies like United Airlines have also got in on the act..

The use of vaccine passports—offering the possibility of a return to (largely) normal life—has also proved an effective strategy in Israel, which has some of the highest rates of COVID-19 vaccination in the world. The app-based “green-pass” system is simple and convenient, with countries like Japan set to implement similar ones in the coming months. The European Union is also set to implement a “Digital Green Certificate” system for vaccinated travellers in the bloc. That ought to be a strong incentive for vaccination as well.

Altogether, behavioural economists are having a field day inventing strategies to motivate the vaccine-wary to get vaccinated. But the single most effective ingredient in reducing vaccine hesitancy worldwide has simply been time, as the US Census Bureau data showed. A series of polls by the Kaiser Family Foundation in the United States also suggests that a significant proportion of the nominally vaccine-hesitant have simply wanted to wait and see what the effects of the vaccines would be on others.

This helps explain the dramatic changes in United States vaccine hesitancy since January, in which time more than half of the country’s adult residents have been fully vaccinated—almost entirely without ill-effect. According to the regular polling of 26 countries by YouGov, this is a global phenomenon, with a notable effect on vaccine hesitancy worldwide (assuming the sample is representative).

Although there is a lot of noise in the signals from individual countries, the population weighted average of YouGov’s polling data shows three clear spikes in vaccine hesitancy since December 2020. The first, in late-December, is probably attributable to an uptick in anxiety after the sudden approval of the first wave of western vaccines (Pfizer-BioNtech, Moderna and Oxford-AstraZeneca).

The second uptick in mid-March, however, perfectly lines up with the initial reports and subsequent European Medicines Agency (EMA) investigation into the relationship between the Oxford-AstraZeneca jab and rare blood-clotting events in vaccine recipients. The final uptick in late-April also matches up perfectly with a similar investigation by the United States Food and Drugs Administration into similar blood-clotting events in recipients of the Johnson & Johnson vaccine.

Fortunately, both these upticks were transient. Nevertheless, that global levels of vaccine hesitancy are so responsive to events like these means that governments and regulatory agencies must continue to tread carefully in their handling of similar safety concerns in the future.

Prospects for the future

That levels of apparent vaccine hesitancy have reduced dramatically worldwide since the beginning of the year is a very encouraging sign. But, in most societies, it is likely that there will continue to be a small subset of the population that refuses to be vaccinated.

That may not be enough to stop some societies from achieving herd immunity—the United Kingdom is a prominent example, as could be the United States—but for others it might, turning herd immunity into mirage, constantly just out of reach. That is unless governments, institutions and businesses are willing to impose measures to make vaccination compulsory. There is already talk of limited compulsory vaccination measures in some places. These are only likely to grow louder in the coming months as vaccine hesitancy becomes the only remaining obstacle to herd immunity in many of the advanced economies.

Nevertheless, even without herd immunity, the exceptionally high levels of vaccine uptake by vulnerable demographics (like the elderly) in most countries means that the COVID-19 pandemic will certainly become more manageable. If the example of Israel is anything to go by, that will allow societies to return to something approaching normality. The world is not there yet, but it will be cause for great celebration when it is—with herd immunity or without.