Public mistrust of vaccines means the world is taking a step backwards in the fight against deadly yet preventable infectious diseases, warn experts.
The biggest global study into attitudes on immunisation suggests confidence is low in some regions.
The Wellcome Trust analysis includes responses from more than 140,000 people in over 140 countries.
The World Health Organization lists vaccine hesitancy as one of the top 10 threats to global health.
Why does it matter?
There is overwhelming scientific evidence that vaccination is the best defence against deadly and debilitating infections, such as measles.
Dr Ann Lindstrand, an expert in immunisation at the WHO, said the current situation was extremely serious.
“Vaccine hesitancy has the potential, at least in some places, to really hinder the very real progress the world has made in controlling vaccine-preventable diseases,” she said.
What about measles?
Countries that were close to eliminating measles have been seeing large outbreaks.
Data shows a rise in cases in almost every region of the world, with 30% more cases in 2017 than 2016.
A decision not to vaccinate, for whatever reason, poses a risk to others as well as the individual from being infected themselves.
If enough people are vaccinated, it stops the disease from spreading through a population – something experts call “herd immunity”.
Imran Khan, from the Wellcome Trust, said: “We are really concerned at the moment because for measles, anything less than 95% coverage can lead to outbreaks and that is what we are seeing.”
Where was trust high?
Most people in lower-income areas agreed vaccines were safe. The highest number was in South Asia, where 95% of people agreed, followed by Eastern Africa, where the figure was 92%.
Rwanda became the world’s first low-income country to provide young women universal access to the HPV vaccine that protects against cervical cancer.
Mr Khan said: “It shows what can be achieved with concerted effort to improve vaccine uptake.”
What makes people sceptical?
In the survey, people with more trust in scientists, doctors and nurses tended to be more likely to agree that vaccines were safe. Conversely, those who had sought information about science, medicine or health recently appeared to be less likely to agree.
In Japan, concerns about the HPV vaccine and a reported link with neurological problems were widely publicised, which experts think knocked confidence in immunisation in general.
Similarly, in France, there was controversy about a pandemic influenza vaccine – accusations that the government bought high quantities of the vaccine and unsubstantiated claims that it had been made too quickly and couldn’t be safe.
Dr Lindstrand said: “One of the most important interventions to counteract doubts and worries about vaccines is to have health workers really well trained and able and ready to recommend vaccinations based on scientific truth and to be able to respond correctly to questions and concerns that parents have and communities have.”