A new study reveals 52 US doctors shared misinformation about COVID-19 on social media and other online platforms, including the claim that "most who took COVID vaccines will be dead by 2025."

Public health researchers from the University of Massachusetts Amherst found physicians in various medical specialties spread false information about COVID-19 vaccines, treatments, and masks, with some reaching large audiences.

"This study was the first, to our knowledge, to identify the types of COVID-19 misinformation propagated by US physicians on social media and the platforms they used, as well as characterize the physicians who spread the misinformation," Sahana Sule and colleagues write in their published paper.

Misinformation has been around long before COVID-19, though its alarming spread during the pandemic potentially exacerbated the consequences of a global public health crisis that's so far killed nearly 7 million people.

About a third of the more than 1 million COVID-19-related deaths in the US by January 2023 were deemed avoidable if public health recommendations had been followed, the authors say.

Sule and team identified media from 2021 and early 2022 containing COVID-19 misinformation attributed to US-based physicians. The 52 doctors were licensed in 29 states, with almost a third of the medical practitioners involved with groups that have been spreading medical misinformation for decades.

Twitter was the most popular platform, with 37 doctors posting misinformation through the site to a combined total of more than 9 million followers. Twenty posted COVID-19 misinformation on five or more social media platforms, and 40 on five or more online platforms like news outlets.

Online misinformation was measured in four categories: medication, vaccines, mask/distancing, and other unsubstantiated or false claims. Most physicians who shared misinformation did so in more than one category.

Some information appeared in contexts that confused or misled. A common claim that most COVID-19 cases were found in people who had been vaccinated is in effect true, but deceiving without also considering most people are vaccinated, and a greater percentage of the few non-vaccinated people are infected.

In December 2022, the death rate for unvaccinated people in the US was estimated to be 271 deaths per 100,000 people. That was more than three times the death rate for fully vaccinated people, at 82 deaths per 100,000 people.

Other unfounded claims included COVID-19 vaccines cause infertility, immune system damage, chronic illness in children, and cancer.

Ivermectin and hydroxychloroquine were widely advertised medications, though randomized clinical trials found they were ineffective at treating COVID-19 infections, and the FDA had not approved them for this use.

Rises in COVID-19 cases in mask-mandated areas were interpreted as evidence that the mandates did not slow infection spread, and despite a lack of evidence, many doctors claimed masks interfered with social development and that school mask mandates were child abuse.

Other misinformation included conspiracy theories about the "plandemic" and that government and public health officials withheld crucial information, inflated statistics to make the virus appear worse, or censored information if it didn't match government advice.

Some said that the virus originated in a Chinese laboratory, contrary to the current scientific evidence when they posted, or that it was leaked from a NIH-funded study and covered up by officials.

With no federal laws about medical misinformation on social media, consumers may struggle to evaluate the accuracy of the assertions made. Most of us don't have the time or energy to research everything ourselves so we trust experts for advice, but what happens when those experts are wrong?

Scientific evidence depends on a body of research that's accumulated over time. The best available research is used to inform practice and guidelines, and transparency, review, and reproducibility are emphasized in the process.

Of course, doctors make mistakes and can be guided by their political views just like everyone else. Yet public health guidance encourages the community to be persuaded by their interpretations of scientific data after years learning about science and our bodies. So why would this small proportion of the over 1 million physicians in the US spread false information that lacked evidence?

Sule and colleagues say understanding motivation requires more research, though they note misinformation propagation has become a lucrative industry. America's Frontline Doctors made at least US$15 million by prescribing hydroxychloroquine and ivermectin for COVID-19 through their $90 per consult telemedicine service.

The study was conducted after social media platforms did begin to combat misinformation, so it may not indicate the full extent of medical misinformation present before then. It may also have missed false misinformation on less-used platforms and didn't capture it in other settings such as clinical care.

"Physicians from a range of specialties and geographic regions have contributed to the infodemic," the team concludes. "High-quality, ethical health care depends on inviolable trust between health care professionals, their patients, and society."

The study has been published in JAMA Network Open.