Trust in vaccines is highest in poorer countries but weaker in wealthier ones where scepticism has allowed outbreaks of diseases such as measles to persist, a global study has found.

France has the least confidence of any country in the world in the safety and effectiveness of vaccines, with a third believing that vaccines are unsafe, according to the study.

The study, led by Wellcome and polling company Gallup, covered 140,000 people from more than 140 countries. It found 6 per cent of parents worldwide - equivalent to 188 million - say their children are unvaccinated. The highest totals were in China at 9 per cent, Austria at 8 per cent and Japan at 7 per cent.

While most parents do choose to vaccinate their children, varying levels of confidence expose vulnerabilities in some countries to potential disease outbreaks, the study’s authors said, recommending that scientists need to ensure people have access to robust information from those they trust.

Public health experts and the World Health Organisation (WHO) say vaccines save up to 3 million lives every year worldwide, and decades of research evidence consistently shows they are safe and effective.

The top health threat

The WHO has specifically identified vaccine hesitancy - which it defines as “the delay in acceptance or refusal of vaccines despite the availability of vaccination services” - as one of the top 10 health threats to the world in 2019.

According to the WHO and UNICEF, gains in the world’s fight against vaccine-preventable diseases are at risk. Lack of confidence in the safety and/or effectiveness of vaccines and the health system, shortages of health workers and supplies, depleted or destroyed health infrastructure, poverty and access difficulties all threaten to disrupt the effectiveness of vaccination programmes.

People’s decision not to vaccinate - for whatever reason - is not just a personal choice of risk-taking; it also poses a risk to others. Being vaccinated protects an individual from being infected themselves, and if enough people are vaccinated, it stops the disease from being spread to the larger population.

What is herd immunity?

This provides what epidemiologists refer to as ‘herd immunity’, or protection from the disease for the entire population, including people who cannot be vaccinated for medical reasons. But for herd immunity to work, a large proportion of the population needs to be vaccinated. How large depends on how contagious the disease is.

For example, approximately 90-95 per cent of the population needs to be vaccinated against measles for herd immunity to work. For less contagious diseases such as polio, the vaccination uptake needs to be 80-85 per cent of the population. For influenza, the figure is closer to 75 per cent for vulnerable groups (very young children, people with chronic illnesses and the elderly). If enough people choose not to vaccinate and to rely on herd immunity for protection, outbreaks of preventable diseases become more common, as we have seen with the recent measles outbreaks in several countries, including the US, India, Brazil and Ukraine.

Why do people disagree on vaccines?

The spread of measles, including in major outbreaks in the US, the Philippines and Ukraine, is just one of the health risks linked to lower confidence in vaccines. In Afghanistan and Pakistan, false rumours about polio vaccines being part of a western plot have in recent years hampered global efforts to wipe out the crippling disease.

Some people living in several higher-income regions were among the least certain about vaccine safety.

In France - a country among several European ones now experiencing outbreaks of measles - one in three disagreed that vaccines were safe, according to the survey. That was the highest percentage for any country worldwide. French people are also among the most likely to disagree that vaccines are effective, at 19 per cent, and to disagree that vaccines are important for children to have, at 10 per cent.

Laws for making vaccines compulsory

In France, a rule has been notified that children will receive 11 compulsory vaccines, up from three prior compulsory shots, or risk being barred from French nurseries or schools. The French government’s announcement seeks to stamp out growing nationwide scepticism towards vaccines and one of the world’s highest vaccine rejection rates.

Neighbouring Italy - where 76 per cent agreed vaccines were safe - recently passed a law that allows schools to ban unvaccinated children, or fine their parents, after immunisation rates dwindled.

UK health secretary Matt Hancock has said he “won’t rule out” the idea of introducing compulsory vaccinations if necessary.

Big leap for Bangladesh and Rwanda

Bangladesh and Rwanda are two of the most notable countries that achieve very high rates of agreement on all three items: vaccine safety, their effectiveness and the importance of children having them. In both countries, success in achieving very high immunisation rates was achieved despite numerous challenges in implementation.

According to the WHO, Rwanda has seen tremendous success and progress in its vaccination programme over the past two decades. In 1995, the national immunisation coverage rate was less than 30 per cent and incidence of vaccine-preventable diseases was very high. Over the past two decades, the authorities have adopted an approach that included working with international partners, local community health workers and adopting technological solutions that could be adapted locally, in order to raise the immunisation coverage rate, which now stands at a remarkable 95 per cent, with gender and geographic equity. The authorities have also successfully introduced six new vaccines into the routine immunisation programme, and the number of vaccine-preventable diseases has dropped significantly.

Other key findings:

* Three-quarters of the world’s people trust doctors and nurses more than anyone else for health advice, and that in most parts of the world, more education and greater trust in health systems, governments and scientists are also a sign of higher vaccine confidence.

* In most regions, people who have high trust in doctors and nurses are very likely to consider that vaccines are safe.

* Globally, eight in 10 people (79 per cent) somewhat or strongly agree that vaccines are safe, while 7 per cent somewhat or strongly disagree.

* 92 per cent of parents worldwide said that their children have received a vaccine to prevent them from getting childhood diseases.