Information from WHO



On 26 May 2021, the COVID-19 subcommittee of the Global Advisory Committee on Vaccine Safety (GACVS) published information on the WHO website related to reported cases of myocarditis following administration of mRNA-based COVID-19 vaccines. 

They indicated that on 17 May 2021, the CDC's COVID-19 Technical Work Group, of the Advisory Committee on Immunization Practices (ACIP), concluded that few cases of myocarditis had been reported to date. These cases appear to occur predominantly in adolescents and young adults, and more often in young men than in young women, most often within four days of receiving the second dose of the vaccine. Most of the cases were mild and continue to be monitored.

The GACVS subcommittee noted that most of the information received so far is based on passive and spontaneous reports, and that more rigorous studies using alternative data sources and stronger study designs, including comparison of vaccinated and unvaccinated populations, are needed in order to assess a possible causal association between the event and the vaccine. Some countries, such as Israel, the United Kingdom, and the United States, will be initiating such studies. The GACVS subcommittee emphasized that it was important to have a harmonized case definition, and that the Brighton Collaboration had recently developed a draft case definition of myocarditis.

While recognizing the clear benefits of mRNA vaccines in reducing deaths and hospitalizations due to infection by the COVID-19 virus, the subcommittee is encouraging health professionals to report all myocarditis and other adverse events observed with these and other vaccines. WHO's COVID-19 Vaccine Safety Surveillance Manual provides guidance to countries on monitoring safety and sharing data regarding adverse events associated with new COVID-19 vaccines.


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