Sept. 10 (UPI) -- Less than 60% of Americans believe vaccines are safe and effective, according to an analysis published Thursday by the Lancet.
Although that figure is on par with much of Western Europe -- and is far higher than those in many eastern European and Asian nations -- it may be "masking pockets of dissent," study co-author Heidi Larson told UPI.
The findings are significant, given the global quest for a vaccine against COVID-19, which as of Thursday afternoon has infected nearly 28 million people globally, including 6.4 million in the United States, based on figures from Johns Hopkins University.
The pandemic won't end until there is a viable vaccine and large numbers of people take it, experts have said.
"Our U.S. data is from a nationally representative sample," said Larson, a professor of anthropology and director of the Vaccine Confidence Project at the London School of Hygiene and Tropical Medicine.
"Based on our social media analysis and other locally specific data collection, those who are overtly against vaccines are more highly organized, and louder, and their messages are having repercussions in different parts of the world," she said.
The Vaccine Confidence Project was founded a decade ago to help monitor public attitudes to vaccines and to inform policymakers of the changing trends and determinants of vaccine confidence around the world.
Public confidence in vaccines varies widely from country to country, according to Larson and her colleagues.
Although signs exist that public trust in preventive vaccines for diseases ranging from the flu to measles may be improving in parts of Europe, several countries -- particularly those experiencing political instability and religious extremism -- are seeing growing skepticism.
In addition, the spread of misinformation online is threatening vaccination programs worldwide, the researchers said.
In 2019, the World Health Organization declared vaccine hesitancy as one of the top 10 threats to global health. Declining public confidence can result in vaccine delays or refusals, which is contributing to outbreaks of vaccine-preventable disease like measles, polio and meningitis, according to Larson and her colleagues.
For their analysis, the researchers mapped global trends in vaccine confidence across 149 countries between 2015 and 2019, using data from more than 284,000 adults worldwide who who responded to 290 national surveys about their views on whether vaccines are important, safe and effective.
The team then estimated trends in public perceptions about the safety and effectiveness of vaccines, and the importance of vaccinating children. It also considered the relationship between vaccine uptake in each country and demographic -- including religious beliefs -- and socioeconomic factors.
Confidence in vaccine safety is increasing in several countries, including Britain, Finland, France, Italy and Ireland, the team reported. In France, where confidence in vaccines has been persistently low, 30% of those surveyed in December 2019 said they believe vaccines are safe -- up from 22% one year earlier.
In Britain, 52% of those surveyed in November 2019 expressed confidence in vaccine safety, up from 47% 18 months earlier, the researchers said.
In the United States, meanwhile, public confidence in vaccines has remained fairly steady, with 50% to 60% of people surveyed believing they are safe, according to the researchers.
Conversely, in Poland, which has a growing anti-vaccine movement, 53% of respondents reported confidence in vaccine safety in 2019, down from 64% in 2015, the data showed.
In other Eastern European countries, fewer than 20% of the public believes vaccines are safe, while in some countries in the Middle East, where some Muslim religious leaders urge followers to not get vaccinated, that percentage is below 5%, according to the researchers.
"Vaccine confidence is highly volatile -- with ups and down, shocks and wobbles -- which means it is vulnerable to crashing, and needs constant vigilance and nurturing to be sustained," Larson said.
Writing in a related commentary, Daniel Salmon and Matthew Dudley, both professors at the Johns Hopkins Bloomberg School of Public Health who were not involved in the study, said that "vaccines have a remarkable safety record, based on rigorous processes of phased randomized controlled trials."
"Without substantial global investment in active vaccine safety surveillance, continuous monitoring of public perceptions and development of rapid and flexible communication strategies, there is a risk of [COVID-19] vaccines never reaching their potential due to a continued inability to quickly and effectively respond to public vaccine safety concerns, real or otherwise," the professors wrote.