Experts are warning that widespread belief in COVID-19 conspiracy theories could make vaccination campaigns less effective when treatments become available.

An international study led by Cambridge University psychologists and social scientists revealed that conspiracy theories linked to the pandemic are widespread, and that people who believe in such misinformation might be less likely to get vaccinated against the novel coronavirus.

"Certain misinformation claims are consistently seen as reliable by substantial sections of the public," said Sander van der Linden, who is director of the Cambridge Social Decision-Making Lab and co-author on the paper. "We find a clear link between believing coronavirus conspiracies and hesitancy around any future vaccine."

The study, which was published this week in the journal Royal Society Open Science, surveyed a total of 5,000 respondents in the United Kingdom, Ireland, Spain, the United States, and Mexico to gauge public perception over the reliability of COVID-19 origin stories, some of which were not evidence-based.

In Mexico, 22 percent of respondents believed that the pandemic is "part of a plot to enforce global vaccination" along with 18 percent in Ireland, Spain and the US, and 13 percent in the UK.

The conspiracy theory that electromagnetic fields from 5G telecommunications towers make COVID-19 symptoms worse was also held by a sizable minority in each nation－16 percent in Mexico and Spain, 12 percent in Ireland, and 8 percent in both the UK and the US.

A damaging and frequently debunked rumor that the novel coronavirus was engineered in a lab in Wuhan, China, was deemed the most valid conspiracy theory among respondents.

In Spain, 37 percent of those surveyed said this claim was "reliable", compared with 33 percent in Mexico, 26 percent in Ireland, and between 22 and 23 percent in the UK and the US.

"As well as flagging false claims, governments and technology companies should explore ways to increase digital media literacy in the population," said van der Linden. "Otherwise, developing a working vaccine might not be enough."

The researchers asked participants to rate the reliability of COVID-19 conspiracy theories on a scale of one to seven. Respondents were also asked about their attitudes to a future COVID-19 vaccine.

The study found that, on average, an increase by one-seventh in perceived reliability of misinformation is associated with a drop of 23 percent in the likelihood they will agree to get vaccinated.

Achieving and maintaining widespread immunity is vital to the eradication or control of disease. Depending on how infectious a disease is, herd immunity can only be achieved if between 50 and 90 percent of a population is immune through natural infection or vaccination, according to the Johns Hopkins Bloomberg School of Public Health.

The Cambridge researchers called on governments to up efforts to confront the spread of misinformation surrounding the novel coronavirus.

Cambridge University has partnered with the UK government on the development of an online game to educate people about the pandemic.

Released this week on the web, Go Viral! drops users into the world of misinformation, and players must then expose the tactics used by malicious actors to spread false claims.