Social media posts have been shared repeatedly with a misleading claim that Pfizer has "only officially admitted" that its Covid-19 vaccine causes side effects such as myocarditis and pericarditis in 2023. The company has in fact stated the conditions as side effects in press statements released as early as 2021 when the vaccine first became available.
The misleading claim was shared on Facebook on October 18, 2023.
"Pfizer has officially admitted that myocarditis and pericarditis are adverse reactions of the Covid-19 vaccine, and that people who have had a severe allergic reaction to any components of the company's vaccine or the Covid-19 vaccine in the past should not be vaccinated with COMIRNATY®," reads the simplified Chinese caption.
The post includes a screenshot of a Pfizer press release and its corresponding Chinese-language translation, as well as a link to the company's website.
The part of the release included in the screenshot states: "Authorized or approved mRNA COVID-19 vaccines show increased risks of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart), particularly within the first week following vaccination. For COMIRNATY, the observed risk is highest in males 12 through 17 years of age".
Misinformation about the safety of Covid-19 vaccines has spread on social media since they were approved for emergency use in 2021. AFP has debunked these claims here.
Myocarditis and pericarditis are most often caused by a viral infection, including Covid-19, and tend to occur among young men (archived link). In most cases, patients' health improves on their own or with the help of treatment.
But Pfizer has stated that heart inflammation is one of the adverse effects from its Covid-19 vaccines since 2021.
Press releases since 2021A keyword search reveals the statement in the misleading post is genuine and was published on October 13, 2023 (archived link).
However, the statement's warning about myocarditis and pericarditis as side effects of the vaccine in the statement is largely a repeat of the same caution given in statements released in November 2021 and January 2022 (archived links here and here).
Health authorities around the world have closely monitored the Pfizer-BioNTech Covid-19 vaccine since its initial authorisation in December 2020 and Pfizer has publicly released information about its adverse effects (archived link).
According to the French Society of Pharmacology and Therapeutics (SFPT), the incidence of myocarditis in vaccinated persons is estimated at 1 per 100,000 persons and 1 per 10,000 in young men (archived link).
A detailed review found that Pfizer has changed its wording about heart inflammation as an adverse effect.
The 2021 and 2022 statements read: "Myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart) have occurred in some people who have received the vaccine, more commonly in males under 40 years of age than among females and older males."
The October 2023 statement reads: "Authorized or approved mRNA COVID-19 vaccines show increased risks of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart), particularly within the first week following vaccination. For COMIRNATY, the observed risk is highest in males 12 through 17 years of age."
Pfizer France told AFP the changes reflect updates made when the vaccine's authorisation was changed from emergency use -- an official process that allowed for an accelerated approval -- to full authorisation.
"These changes do not reflect new information or data on cases of myocarditis or pericarditis".
Pfizer France also noted the European Medicines Agency (EMA) had issued a recommendation in July 2021 about listing myocarditis and pericarditis in the product information of Covid-19 vaccines by Pfizer and US pharmaceutical company Moderna.
More common after infectionIn fact, it is more likely for a person infected with Covid-19 than a person that has received the vaccine to develop myocarditis.
A meta-analysis published in August 2022 found the risk of myocarditis "is more than seven-fold higher in persons who were infected with the SARS-CoV-2 than in those who received the vaccine" (archived link).
The researchers also concluded that "the outcomes of myocarditis after vaccination were less severe than for other types of myocarditis."
"Looking at the risks, the benefits of vaccination are not in doubt for women and men over age 30, and the data on myocarditis since summer 2021 certainly does not mean we should stop vaccinating men under 20 or 30 years of age, who still benefit from a decline in serious events links to Covid," said French cardiologist Florian Zores in a blog post.