Researchers indicated that in a review of the data from the first 6 months after initiation of the mRNA COVID-19 vaccines, the reported adverse effects were generally mild and short-lived.

In a recent publication in The Lancet Infectious Diseases, researchers conducted an observational study and analyzed data reported to the Vaccine Adverse Event Reporting System (VAERS), a passive system, and v-safe, a new active system, during the first 6 months of the U.S. COVID-19 vaccination program. The data reported was during December 14, 2020, to June 14, 2021.

VAERS reports were categorized as nonserious, serious, or death. Reporting rates were calculated using numbers of COVID-19 doses administered as the denominator. Researchers examined v-safe survey reports from Days 0 to 7 after vaccination for reactogenicity, severity (mild, moderate, or severe), and health impacts (i.e., unable to perform normal daily activities, unable to work, or received care from a medical professional).

The researchers found that 298.7 million doses of mRNA vaccines were administered in the U.S. during the study period, and VAERS processed 340,522 reports. Of those, 313,499 (92.1%) were nonserious; 22,527 (6.6%) were serious (nondeath); and 4,496 (1.3%) were deaths.

Data from v-safe participants revealed that more than half (about 71%) of the 7.9 million participants reported local or systemic reactions, more commonly after dose 2 than after dose 1. Of those reporting reactions after dose 1, about two-thirds (68.6%) reported a local reaction and 52.7% reported a systemic reaction. Other reported findings included injection-site pain occurred after dose 1 in 66.2% of participants and 68.6% after dose 2. An estimated one third of participants (33.9%) reported fatigue after dose 1 and 55.7% after dose 2. Headache was reported among 27% of participants after dose 1 and 46.2% after dose 2. Injection-site pain, fatigue, or headaches were typically reported in the first week after vaccination.

Reports of being unable to work or to perform normal daily activities, or instances of seeking medical care, occurred more frequently after dose 2 (32.1%) than after dose 1 (11.9%). Fewer than 1% of participants reported seeking medical care after dose 1 or 2 of the vaccine. Reactions and health effects were reported more often in female than in male recipients and in individuals aged younger than 65 years compared with older individuals. Serious adverse events, including myocarditis, were identified, but considered as a rare occurrence.

The authors wrote, "In this analysis of VAERS and v-safe data from the first 6 months of COVID-19 vaccination rollout in the USA, when over 298 million doses of mRNA vaccines were administered, we found that reactogenicity was similar to what was reported from clinical trials and from early post-authorization monitoring. In both VAERS and v-safe, local injection-site and systemic reactions were commonly reported."

They concluded that safety data from more than 298 million doses of mRNA COVID-19 vaccine administered in the first 6 months of the U.S. vaccination program reveal that most reported adverse events were mild and short in duration.

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