One of the predicates of anti-Covid-vaxxers insinuations such as
"NEW - FDA orders Pfizer, Moderna to update COVID mRNA vaccine warnings, adding heart injury risk, ..." is the difficulty of finding evidence from the time frame of the claim. In this case, the difficulty of finding official instructions about the three Covid vaccines used in the 2021 and 2022 time frame. Well with DDG, a well composed search phrase, and a little patience (in alphabetical, not chronological, order of authorization):
Janssen / Johnson & Johnson, from the FDA,
2021,
https://www.fda.gov/media/146305/downloadMyocarditis and Pericarditis
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. In most of these people,
symptoms began within 8 days following vaccination. The chance of having this occur is very low.
You should seek medical attention right away if you have any of the following symptoms after
receiving the vaccine:
• Chest pain
• Shortness of breath
• Feelings of having a fast-beating, fluttering, or pounding heart
Moderna, June/17/2022,
https://www.memorialcare.org/sites/default/files/_images/content/coronavirus/vaccine-resources/MHS_VaccineClinics_ModernaEUARecipientFactSheet12yandOlder_2022_06_17.pdfSide effects that have been reported during post-authorization use of the vaccine include:
• Severe allergic reactions
• Myocarditis (inflammation of the heart muscle)
• Pericarditis (inflammation of the lining outside the heart)
• Fainting in association with injection of the vaccine
Among the listed possible contra-indications for receiving the Moderna vaccine are:
have had myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of
the lining outside the heart)
Pfizer, 8 December 2022,
https://labeling.pfizer.com/ShowLabeling.aspx?id=14472Side effects that have been reported with these vaccines include:
Severe allergic reactions
Non-severe allergic reactions such as rash, itching, hives, or swelling of the face
Myocarditis (inflammation of the heart muscle)
Pericarditis (inflammation of the lining outside the heart)
Among the listed possible contra-indications for receiving the Pfizer vaccine are:
have had myocarditis (inflammation of the heart muscle) or pericarditis
(inflammation of the lining outside the heart)
Information was not "denied" or "withheld".BTW, contrary to one anti-Covid-vaxxer claim, the pre-approval Pfizer vaccine and the approved "Comirnaty" were, at the time of approval, the same vaccine. "Comirnaty" was just the FDA-approved trade name. Whether the anti-Covid-vaxxers were ignorant or deceivers playing on others' lack of knowledge, I do not know.