U.S. essential and frontline workers in a six-state study had significantly milder infections and lower viral loads after receiving a COVID-19 mRNA vaccine than their unvaccinated peers.
That’s according to a new study of nearly 1,200 workers, including healthcare personnel, from Arizona, Florida, Minnesota, Oregon, Texas and Utah. Study participants tested positive for COVID-19 and received two to three doses of mRNA vaccines before an infection with the delta variant, and three doses before infection with the omicron variant.
Investigators analyzed data from weekly self-collected nasal swabs and genome sequencing results from frontline workers infected between Dec. 14, 2020, and April 19, 2022. Participants’ health outcomes were followed until May 2022.
Results revealed multiple apparent benefits of recent vaccination with two or three mRNA vaccine doses less than 150 days before infection with either variant. Vaccinated study participants had fewer symptoms, shorter illness duration, less medical care seeking or lower viral load when compared with their unvaccinated peers for some comparisons. However, the precision and statistical significance of specific estimates varied, the researchers noted.
In addition, symptomatic participants had significantly higher average viral loads than those with no symptoms. Previous studies have suggested that high viral loads are associated with increased transmission.
Full findings were published in JAMA.
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