mRNA COVID-19 vaccines were not associated with significantly higher rates of 23 serious adverse events 1 to 21 days after receiving one or two doses than after 22 to 42 days, finds an interim analysis of surveillance safety data involving millions of people today in JAMA.No association between the vaccines and the specified outcomes met the criteria for a safety signal, the study authors said.Researchers from Kaiser Permanente Vaccine Study Center led the study, which consisted of analyzing vaccine surveillance data from the Vaccine Safety Datalink (VSD) on 6.2 million vaccinated members of eight US health plans from Dec 14, 2020, to Jun 26, 2021.