Anti-vaccine study resurfaces misleading myocarditis claims

This week, a shingles vaccine study drew mixed reactions online and an ongoing hepatitis A outbreak in California fueled anti-vaccine speculation.

This week, online vaccine conversations focused on three vaccine studies of varying credibility. Several popular vaccine opponents questioned a dubious study about COVID-19 vaccines and myocarditis with ties to an anti-vaccine organization. Meanwhile, a large-scale study that found shingles vaccination reduces the risk of heart attack, stroke, and other cardiovascular events was dismissed by some as a “scam.” Finally, social media users spread conspiracy theories about the hepatitis A outbreak in Los Angeles County.

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What’s trending in vaccine conversation:

A dubious new study authored by an anti-vaccine organization claims without evidence that myocarditis linked to mRNA COVID-19 vaccines is more widespread than reported. The study’s authors are well-known anti-vaccine figures who have promoted several conspiracy theories, including that COVID-19 vaccines cause “turbo cancer.” Many online vaccine opponents promoted the study on social media, calling it “the most definitive myocarditis paper.” Some posts claim that the review proves that mRNA vaccines are unsafe. Although the journal claims to be peer-reviewed, it does not appear to be a legitimate academic publication. The editor in chief, who also co-authored the study, is a former physician whose medical credentials were revoked for promoting false claims about COVID-19 and who now sells hoax vaccine detox products. Additionally, the journal is not found in the National Library of Medicine, the Directory of Open Access Journals, or other publication databases. 

A new study of over a million older adults found that shingles vaccination was associated with a 23 percent reduction in the risk of cardiovascular events, like heart attack and stroke, for up to eight years after vaccination. This follows four studies in the last two years showing that shingles vaccination is linked to a decreased risk of dementia, including Alzheimer’s disease. The study received widespread media coverage and attention online. Some social media users dismissed the research as a “scam”, claiming without evidence that shingles vaccines are dangerous and that this is a plot to trick people into getting vaccinated. Other commenters called all vaccines poisons and alleged that mRNA vaccines are killing people. One post suggested that the study is a way to promote “new” vaccines because no one wants the “coronavirus jab,” despite the fact that the shingles vaccine in the study has been in use since 2006.

On May 5, the Los Angeles County Department of Public Health declared a hepatitis A outbreak. The number of reported cases tripled from 2023 to 2024, and the 29 cases reported in the first three months of 2025 is twice the number reported during the same period last year. Notably, most of the cases reported this year were in people without known risk factors for hepatitis A infection, such as international travel and experiencing homelessness. Health officials encouraged residents to check their vaccination status and wash their hands regularly. Many social media users shared information about the virus and tips to stay safe and promoted hepatitis B vaccination. Others downplayed the outbreak, blamed migrant and homeless populations, and accused health officials and the media of fearmongering. Several commenters claimed without evidence that vaccines caused the outbreak, that the outbreak is a plot to make people get vaccinated, and speculated that either COVID-19 or COVID-19 vaccines have weakened people’s immune systems, making them more susceptible to disease.

Read the fact checks: 

• Public Good News: Most of what you know about myocarditis is wrong
• CDC: Shingles Vaccination
• CHOP: Hepatitis A: The Disease & Vaccines

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Recommendations for public health professionals

Each week the Infodemiology.com team will provide messaging recommendations in response to some of the trending narratives outlined above. These helpful tips can be used when creating content, updating web pages and FAQs, and to inform strategy for messaging about vaccines.

Vaccine opponents often use questionable research to spread anti-vaccine narratives. Debunking messaging may explain that vaccination is the best protection against COVID-19. Talking points may emphasize that COVID-19 infections can increase the risk of cardiovascular issues, while COVID-19 vaccination reduces the risk of heart attack and stroke.

A new study is the latest to show additional benefits of shingles vaccination, but some remain hesitant about the vaccine. Messaging may emphasize that vaccination is the only way to prevent shingles and that the vaccine is over 90  percent effective. Communicators may also wish to explain that research in the last few years suggests that shingles vaccination is also linked to a reduced risk of heart attack, stroke, and dementia.

The ongoing hepatitis A outbreak in Los Angeles County underscores the importance of vaccination to prevent disease spread. Communicators may explain that hepatitis A can affect anyone who is not vaccinated and that vaccination protects children and other vulnerable groups from the potentially serious liver infection. Messaging may emphasize how the virus spreads, who is most at risk, and how to prevent infection through vaccination and good hygiene practices.

Interested in recommendations tailored to health care providers? Click here.