“As of July 12, 2021, 1,047 reports of myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the outer lining of the heart) had been reported in people under age 30, particularly in male teens and young adults, after vaccination with the Pfizer/BioNTech or Moderna mRNA vaccines The CDC’s Advisory Committee on Immunization Practices (ACIP) has said available data "suggest likely association of myocarditis with mRNA vaccination in adolescents and young adults." Even with the increased risk, heart inflammation is a rare occurrence.”

https://www.health.harvard.edu/covid-19-vaccines

Most people read the headline only or spend about 15 seconds reading an online article never reading the entire thing. Interesting that the data on myocarditis was put as the last item of the article and the top portion only says adverse events are rare and educated on common side effects.

https://www.washingtonpost.com/news/the-intersect/wp/2016/06/16/six-in-10-of-you-will-share-this-link-without-reading-it-according-to-a-new-and-depressing-study/

CDC lists rare reactions from covid 19 vaccine 

https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/safety-of-vaccines.html

"Cases of apparent secondary immune thrombocytopenia (ITP) after SARS‐CoV‐2 vaccination with both the Pfizer and Moderna versions have been reported and reached public attention. Public alarm was heightened following the death of the first identified patient from an intracranial hemorrhage, which was reported on the Internet, then in USA Today 1 and then in The New York Times. 2 Described below, we have collected a series of cases of very low platelet counts occurring within 2 weeks of vaccination in order to enhance our understanding of the possible relationship, if any, between SARS‐CoV‐2 vaccination and development of ITP with implications for surveillance and management."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8014568/

“Adverse events from drugs and vaccines are common, but underreported. Although 25% of ambulatory patients experience an adverse drug event, less than 0.3% of all adverse drug events and 1-13% of serious events are reported to the Food and Drug Administration (FDA). Likewise, fewer than 1% of vaccine adverse events are reported. Low reporting rates preclude or slow the identification of “problem” drugs and vaccines that endanger public health.”

https://digital.ahrq.gov/sites/default/files/docs/publication/r18hs017045-lazarus-final-report-2011.pdf

Harvard Pilgrim Healthcare is affiliated with Harvard Medical School and was asked by HHS to conduct this study.

https://www.covidlonghaulers.com

https://covid19criticalcare.com/wp-content/uploads/2021/06/FLCCC-Alliance-I-RECOVER-Management-Protocol-for-Long-Haul-COVID-19-Syndrome.pdf

https://regenerativemedicinela.com/

Antiphospholipid antibodies (aPLs), present in 1-5 % of healthy individuals, are associated with the risk of antiphospholipid syndrome (APS), which is the most common form of acquired thrombophilia. APLs may appear following infections or vaccinations and have been reported in patients with COronaVIrus Disease-2019 (COVID-19). However, their association with COVID-19 vaccination is unclear. Notably, a few cases of thrombocytopenia and thrombotic events resembling APS have been reported to develop in recipients of either adenoviral vector- or mRNA-based COVID-19 vaccines. The aim of this review is therefore to speculate on the plausible role of aPLs in the pathogenesis of these rare adverse events. 

https://pubmed.ncbi.nlm.nih.gov/34090785/