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Analysis of data from 6.2 million people has found no significant associations between mRNA COVID-19 vaccines and serious side effects. The study authors, based in cities across the United States, undertook this study to compare mRNA vaccines’ negative effects in the first 21 days post-vaccination to negative effects occurring 22 days + after vaccination.
Safe and effective vaccines against SARS-CoV-2 are critical to ending the pandemic. Rare or serious outcomes associated with a vaccine may not be identified in phase 3 trials for many reasons, including limited sample size, restrictive inclusion criteria, limited duration of follow-up, and trial participants who may differ from the population ultimately receiving the vaccine. Furthermore, there is limited experience with mRNA platforms. Surveillance is critical to ensure safety, maintain trust, and inform policy. You can read more about the study here https://jamanetwork.com/journals/jama/fullarticle/2784015