2020Sept. 22, 2020: U.S. Centers for Disease Control and Prevention (CDC) identifies myocarditis as an adverse event of special interest, or a potential side effect.
December 2020: One case of pericarditis reported to the U.S. Vaccine Adverse Event Reporting System (VAERS), which is co-managed by the CDC and FDA.
20212021: Myocarditis cases spike in the U.S. military.
January 2021: 28 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS.
January 2021: First cases of postvaccination myocarditis recorded in Israel.
February 2021: 64 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including two deaths.
Feb. 24–25, 2021: CDC meets with its advisers but does not discuss COVID-19 vaccines.
Feb. 27, 2021: FDA authorizes Johnson & Johnson's COVID-19 vaccine.
March 2021: 54 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS.
March 2, 2021: CDC recommends Johnson & Johnson's COVID-19 vaccine for adults.
March 3, 2021: Israeli authorities meet with hospital officials to discuss postvaccination heart problems.
March 5, 2021: FDA holds meeting with its advisers. Myocarditis is not discussed.
March 6, 2021: Rutgers University becomes first major US school to announce COVID-19 vaccine mandate.
April 2021: 158 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS.
April 2021: CDC holds multiple public meetings with no discussion of myocarditis.
April 5, 2021: Israeli officials brief the CDC on postvaccination myocarditis cases.
April 7, 2021: U.S. government call covers myocarditis cases recorded in military members after vaccination.
April 23, 2021: Israeli Ministry of Health report on postvaccination myocarditis identifies two deaths, Israeli media report. The second deceased was a previously healthy 35-year-old man. Among men aged 18 to 30, there is a one in 20,000 probability of developing myocarditis, the report found. "It seems that these events can be a signal of a possible connection to the vaccine," the committee said. The findings were sent to the FDA.
April 27, 2021: CDC officials privately acknowledge that processing of VAERS reports is "taking longer than usual."
April 27, 2021: CDC officials say 24 cases of myocarditis were identified in VSD.
April 28, 2021: France detects safety signal for postvaccination myocarditis.
April 28, 2021: CDC director receives notes from discussion with military on myocarditis cases.
April 30, 2021: FDA receives Pfizer report noting myocarditis cases in Pfizer's database.
May 2021: 487 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including four deaths.
May 2021: CDC forms a team to review medical records for reported cases of postvaccination myocarditis.
May 5, 2021: CDC meets with advisers but doesn't discuss COVID-19 vaccines.
May 12, 2021: Myocarditis is not discussed during meeting on Pfizer's COVID-19 vaccine. Dr. Tom Shimabukuro, a CDC official, gives a presentation on blood clotting after Johnson & Johnson vaccination.
May 12, 2021: Dr. Walensky recommends Pfizer's vaccine for virtually all children aged 12 to 15, based on advice from advisers.
May 13, 2021: CDC officials told to direct questions on potential myocarditis cases to two top vaccine safety officials, Drs. John Su and Shimabukuro.
May 13, 2021: Children's National in Washington registers two suspected cases.
May 16, 2021: CDC official says in email, "we are hearing quite a lot about this now, and I don't have a clear understanding of what is and has been being done."
May 28, 2021: Nine postvaccination myocarditis cases from one state not reported to VAERS, according to CDC.
June 2021: 752 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including five deaths.
June 2021: Some experts start calling on U.S. authorities to pause COVID-19 vaccination of young, healthy people.
June 10, 2021: "I think the myocarditis is something that needs to be looked at closely because we’re likely seeing the tip of the iceberg," says Dr. Michael Kurilla of the U.S. National Institutes of Health, another FDA adviser. June 10, 2021: Pfizer spokesperson tells news outlets that "the benefit-risk profile of our vaccine remains positive."
July 2021: 364 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including seven deaths.
July 22, 2021: CDC says it confirmed 282 postvaccination myocarditis cases in people aged 18 to 29.
August 2021: 311 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including seven deaths.
Aug. 23, 2021: Excess myocarditis risk for vaccinated males aged 16 or 17 "approaching 200 cases per million," FDA discloses, based on data from Optum health care claims database.
Aug. 30, 2021: One myocarditis case and one pericarditis case occurred among vaccinated trial participants, Pfizer reveals.
Aug. 30, 2021: Highest rate of reported myopericarditis cases within seven days of a shot was 71.5 cases per million second Pfizer doses among boys aged 16 or 17, according to the CDC.
Aug. 30, 2021: Benefits of Pfizer's vaccine continue to outweigh the risks, CDC officials say. They estimate every million Pfizer shots among 16- to 17-year-olds will cause 73 cases of myocarditis but prevent more hospitalizations.
September 2021: 377 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including 10 deaths.
Sept. 2, 2021: 654 reports of myocarditis or pericarditis in Pfizer's safety database, company says. Seventy-seven reports of myocarditis or myocarditis and pericarditis in Moderna's safety database, company says. Some patients, including a young male, died or had not recovered.
Sept. 2, 2021: Based on the reports and other data, a causal association between myocarditis/pericarditis and the mRNA vaccines is "considered of at least a reasonable possibility," the European Medicines Agency says.
Sept. 9, 2021: U.S. President Joe Biden and his administration announce COVID-19 vaccine mandates for tens of millions of Americans, including many young, healthy people.
Sept. 15, 2021: Hong Kong changes recommendation from two doses of Pfizer to one dose after spike in myocarditis cases.
Sept. 22, 2021: One case of myocarditis reported after Pfizer booster, CDC official says. Not possible to determine the risk of rare side effects like myocarditis after boosting, CDC safety committee says.
Sept. 22, 2021: V-safe does not collect information on myocarditis, CDC official admits.
Sept. 23, 2021: CDC officials say they don't know how many cases of myocarditis booster shots will cause. They project up to 26 cases per million boosters in 18- to 29-year-olds, but say more COVID-19 cases and hospitalizations would be prevented.
Sept. 29, 2021: CDC meets on non-COVID vaccines.
October 2021: 321 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including five deaths.
Oct. 8, 2021: Iceland suspends use of Moderna's vaccine due to the heart inflammation.
Oct. 14, 2021: FDA says more myocarditis/pericarditis cases have been reported to its Biologics Effectiveness and Safety Initiative system.
Oct. 21, 2021: The U.S. Department of Veterans Affairs has identified 7 post-vaccination myocarditis cases, CDC publicly discloses, but no signal was established and all cases resolved.
Oct. 21, 2021: About a quarter of cases in people 29 or younger reviewed in VAERS were not known to have recovered, according to available data, with 19 still hospitalized.
Oct. 22, 2021: Rates of reported cases among males aged 18 to 24 approximately 139 per million after Moderna second dose and 43 per million after Pfizer second dose, French researchers say.
Oct. 26, 2021: CDC cardiologist Dr. Matthew Oster says "we don't know a whole lot" about myocarditis after COVID-19 vaccination. "We really need to see what the long-term outcomes for these kids will be," he added later.
Oct. 26, 2021: Dr. Michael Nelson, an FDA vaccine adviser, says he's concerned that some cases of postvaccination myocarditis aren't being reported.
November 2021: 267 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including six deaths.
Nov. 2, 2021: Of postvaccination myocarditis patients who received cardiac MRIs, 72 percent had abnormal results, official says. Of patients who responded to CDC survey, 48 percent reported symptoms persisting after three months.
Nov. 18, 2021: Reported cases of myocarditis as high as 117 per million after doses of Moderna, and 47 per million doses of Pfizer, among males aged 18 to 29, German researchers say.
Nov. 26, 2021: Six people were reported to have died with myocarditis or pericarditis after Pfizer vaccination, the Netherlands Pharmacovigilance Centre Lareb reports. Other causes were found for two of the deaths.
December 2021: 304 cases of myocarditis, pericarditis, or myopericarditis reported to VAERS, including five deaths.
Dec. 16, 2021: Eight cases of myocarditis among children aged 5 to 11 confirmed, including one in a 6-year-old male, CDC official says.
Dec. 18, 2021: 26-year-old New Zealand man's death ruled as being caused by vaccine-induced myocarditis following an autopsy.
2022Jan. 3, 2022: Non-vaccine causes of death ruled out in death of 57-year-old New Zealand woman who experienced myocarditis after COVID-19 vaccination, researchers report.
Jan. 5, 2022: Rate of myocarditis in Israel after Pfizer vaccination reported as high as 153 per million second doses among males aged 16 to 19.
Jan. 19, 2022: Rates of reported cases in the United Kingdom as high as 71 per million second Moderna doses among people aged 18 to 29.
Feb. 4, 2022: Rates of reported VAERS myocarditis cases as high as 40 per million second doses among 18- to 24-year-olds within seven days of vaccination, CDC official says. Most patients were hospitalized and discharged but 30 percent were not known to have recovered.
Feb. 4, 2022: Excess cases of myocarditis up to 61.8 per million within seven days of second Moderna doses in males, according to data from VSD.
Feb. 4, 2022: Excess risk of myocarditis 9.8 times higher after a Moderna second dose among males aged 12 to 39 when compared to the unvaccinated, Danish officials report to the CDC.
Feb. 4, 2022: Data now show an "association of myocarditis" with Moderna's vaccine and young people, CDC safety committee says. Group says it will continue to review data on myocarditis after vaccination.
Feb. 4, 2022: Lower rates of myocarditis recorded when the space between the two primary series doses is extended, Canadian researchers tell CDC.
April 6, 2022: Israel has recorded 213 cases of postvaccination myocarditis, official says.
April 20, 2022: Number of reported cases in VAERS rises to 148 within seven days of a booster, CDC official reports. The highest rate is 23.2 cases per million Pfizer booster doses among people aged 16 or 17. Most patients were hospitalized but all were discharged.
April 20, 2022: Reported cases in U.S. Department of Veteran Affairs system up to 40; chart review confirmed 15.
May 17, 2022: Hong Kong authorities opt to compensate family of 66-year-old woman who died from myocarditis after Pfizer vaccination.
May 19, 2022: Reported rates of myocarditis within seven days of vaccination as high as 74.2 per million after a second dose of Pfizer's vaccine among males 16 or 17. Rates for males are 48.1 for 12 to 15 and 35.3 for 18 to 24.
May 19, 2022: As CDC panel of advisers votes in support of Pfizer booster for ages 5 to 11, adviser Veronica McNally says parents should know rates of myocarditis are lower after a booster and that the booster will increase protection.
June 7, 2022: Reported rates of myocarditis higher than expected in males as young as 5 and as old as 49, CDC says. The number of verified cases ending in deaths is up to 21, but CDC says none of the deaths have been confirmed as having been caused by the myocarditis.
June 7, 2022: Survey of health care providers who cared for patients estimated 18.3 percent had not fully recovered months later. Available information indicates most people "recover from myocarditis by 3-8 months after diagnosis," Dr. Shimabukuro says, but "there can be long-term effects."
June 7, 2022: Novavax says five cases of myocarditis happened in vaccinated volunteers in its COVID-19 vaccine trials.
June 23, 2022: 37 percent of patients whose health care provider responded to a CDC survey were not confirmed to be fully recovered at least 90 days after diagnosis.
June 23, 2022: Myocarditis meets safety signal criteria in VSD for boosters from Pfizer and Moderna, CDC panel told. Excess cases as high as 200.3 per million boosters among males 16 or 17, which is higher than the second dose rate. Many patients were hospitalized but all were discharged.
June 23, 2022: Dr. Sarah Long, a CDC adviser, expresses surprise with the myocarditis rate following a booster.
June 23, 2022: Likely patients who suffered myocarditis after a first dose, got vaccinated again, and suffered myocarditis again, CDC official says.
July 13, 2022: FDA authorizes Novavax's COVID-19 vaccine even after finding evidence that the vaccine increased the risk of myocarditis and pericarditis.
July 19, 2022: Number of confirmed VAERS myocarditis reports up to 1,321, with another 515 ruled out or still under review. Highest rate remains 75.9 per million second doses administered to males 16 or 17. Highest excess case rate in VSD is 62.8 per million Moderna second doses in 18- to 39-year-old males.
July 19, 2022: CDC recommends Novavax's vaccine for adults.
Sept. 1, 2022: No reports of myocarditis to VAERS among young children, CDC official says. Higher rates than expected, as high as 21.6 per million among males 16 or 17, within seven days of a booster for males aged 12 to 29.
Sept. 1, 2022: Myocarditis rates in VSD as high as 189 per million for males aged 16 or 17 after a booster, which is higher than the 137 per million after a second dose.
Oct. 4, 2022: Rate of reported myocarditis cases in VAERS higher after booster for young males than after second dose, CDC officials disclose.
2023Jan. 3, 2023: Eight sudden cardiac deaths in Qatar after COVID-19 vaccination determined to likely be from the vaccination.
Feb. 22, 2023: Singapore says it will pay family of man who died with myocarditis after COVID-19 vaccination.
Feb. 24, 2023: One case of myocarditis after bivalent vaccination detected in VSD, CDC official says.
Feb. 24, 2023: Risk of myocarditis after a bivalent shot is unknown, CDC official says.
Feb. 27, 2023: Family of young girl who died from myocarditis after Pfizer vaccination to be compensated, Taiwanese authorities say.
March 15, 2023: FDA adds warning about myocarditis to fact sheets for Johnson & Johnson's vaccine.
April 10, 2023: Switzerland opts against recommending COVID-19 vaccines for citizens due to high levels of previous infection and/or vaccination.
May 11, 2023: COVID-19 public health emergency ends, but vaccines are still available under emergency authorization.
June 1, 2023: U.S. government compensates third person for myocarditis caused by COVID-19 vaccination.
June 13, 2023: CDC claims no postvaccination deaths have been caused by myocarditis.
June 30, 2023: Deadline for Moderna's subclinical myocarditis study passes without publication.
Aug. 3, 2023: Pfizer officials tell Australian Senate it doesn't know why company's vaccine inflames the heart.
Sept. 12, 2023: Two cases of myocarditis or pericarditis after bivalent vaccination in VSD, CDC officials report.