Closeup image of senior woman getting temperature check with an infrared thermometer; Credit: GettyImages-1256717963.jpg

New federal data shows that adults aged 50 years and older who received a second COVID-19 mRNA booster dose have less frequent injection site and systemic reactions than after a first dose with the same vaccine, the Centers for Disease Control and Prevention reported Thursday.

Investigators looked at adverse vaccination events reported by people using the CDC’s V-safe and Vaccine Adverse Event Reporting System (VAERS) from March 29 and July 10, 2022. They included only reports from adults who received the same brand of vaccine. In addition to a low and less frequent rate of adverse events with a second dose, 95% of the more than 8,000 events reported in the study time frame were not serious. Among both nonserious and serious reports to VAERS, COVID-19 was the most commonly reported adverse event.

Serious adverse events

The findings are consistent with those of a small clinical study of second boosters in participants who received either Pfizer-BioNTech (154) and Moderna (120) vaccines, the CDC noted. That study did not find any unexpected safety concerns.

“Health care providers and patients should be aware that local and systemic reactions are expected after a second mRNA COVID-19 booster dose,” investigators wrote in their report. “Serious adverse events are uncommon.”

Different results for LTC residents

The results were quite different in a recent long-term care facility study of 280 residents, which found that third-dose COVID-19 vaccine recipients had greater odds of adverse events. That study compared adverse reactions after receipt of different vaccination brand combinations. 

One factor that may have influenced the findings of the larger CDC study is that older adults are less likely than younger adults to report adverse vaccination-related events, the CDC reported.

The Food and Drug Administration in March 2022 authorized a second mRNA booster dose at four or more months after receipt of a first booster dose for adults aged 50 years of age and older and for people with moderate to severe immune compromising conditions. 

Approximately 16.8 million Americans in this age group received a fourth dose of a COVID-19 vaccine during the CDC study period. Reports to the VAERS and V-safe programs may not represent the entire population of vaccine recipients who experience adverse vaccine reactions, CDC investigators noted.

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