This is a literature report for the following literature source(s): . A patient (no qualifiers provided) received BNT162b2 (BNT162B2), as dose 3 (booster), single (Batch/Lot number: unknown) for covid-19 immunisation. The patient's relevant medical history and concomitant medications were not reported. Vaccination history included: Bnt162b2 (Dose 1), for COVID-19 immunisation; Bnt162b2 (Dose 2), for COVID-19 immunisation. The following information was reported: MYOCARDITIS (medically significant), outcome "unknown". The patient underwent the following laboratory tests and procedures: Cardiac monitoring: myocarditis; laboratory data: unknown results; Troponin I: above the upper limit of normal. Clinical course: The COVID-19 mRNA vaccines are effective in reducing COVID-19-related severe disease and death. Waning vaccine effectiveness has prompted the recommendation to administer additional (booster) doses. Third-dose vaccination is associated with improved protection. Recent studies suggest some individuals benefit from receiving a fourth dose. With additional doses of COVID-19 mRNA vaccines being recommended, it is essential to monitor its safety. Myocarditis has been reported following COVID-19 mRNA vaccination. Studies showed the rates of myocarditis to be highest after the second dose. Whether administration of a third vaccination dose further increases the risk of myocarditis is not known. This study aimed to evaluate whether a third dose of COVID-19 mRNA vaccine was associated with an increased risk of myocarditis. Findings: Of 3,076,660 members who received at least one dose of COVID-19 mRNA vaccines, 2,916,739 (94.5%) received at least two doses, and 1,146,254 (47.0%) received three doses. Table 1 shows the baseline characteristics. Median age was 47 years- 53.6% were women, 29.7% one race, 7.1% another race, 38.8% another race, and 13.3% were from another race. 1,673,672 (54.5%) received at least one dose of BNT162b2, and 1,490,941 (48.5%) received at least one dose of mRNA-1273. Within 21 days after vaccination, there were 6 cases of myocarditis following the first dose, 26 cases following the second dose, and 9 cases following the third dose. The incidence rate ratio for myocarditis was 0.86 (95% CI 0.31-1.93) for the first dose, 4.22 (95% CI 2.636.53) for the second dose, and 2.61 (1.13-5.29) for the third dose/ Most myocarditis cases following the second and third dose occurred within seven days of vaccination. The increased incidence was observed primarily among patients younger than 40 years. Of the nine cases of myocarditis following the third dose, eight were men, and five were between 18 and 40 years of age. Median follow-up was 224 days. During the follow-up period, one patient died from events unrelated to myocarditis (cancer). All other myocarditis cases was still small, limiting the precision of the point estimates. Fifth, myocarditis cases were identified using ICD codes, so cases not diagnosed as myocarditis by the primary clinician would have been missed. Finally, no causal relationship between COVID-19 mRNA vaccination and post-vaccination myocarditis can be established, given the observational nature of this study. Sender's Comments: Based on the current available limited information in the case provided, the causal association between the event myocarditis and the use of suspect product BNT162b2 cannot be fully excluded. The case will be reassessed once further information is available. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to RAs, Ethics Committees, and Investigators, as appropriate.