Study Finds Millions of mRNA Vaccines Produced No Immediate Severe Side Effects

Study Finds Millions of mRNA Vaccines Produced No Immediate Severe Side Effects

Photo: BELCHONOCK/DepositPhotos

The concerted efforts of the world's scientists produced multiple vaccines for COVID-19 in record speed. This unprecedented success was possible due in large part to advances in mRNA vaccine technology which had already been many years in the making. The two mRNA vaccines distributed in the United States—Moderna and Pfizer/BioNTech—are incredibly effective at preventing the contraction, spread, and most serious cases of COVID-19. A recent study published in JAMA found that of 6.2 million individuals, no severe side effects seem to have occurred as a result of the vaccine within the weeks following the jabs.

The study was funded by the Center for Disease Control's Vaccine Safety Datalink. A team of researchers examined data from 11.8 million doses of the two mRNA vaccines spread over 6.2 million people. The team noted event rates (or frequency) of 23 serious health outcomes—including heart attack, stroke, blood clots, and Guillain-Barré syndrome. Two discrete time periods were considered, the first 21 days post jab, and the following 21 days until the 42nd day after vaccination.

The event rates “were not significantly higher for individuals 1 to 21 days after vaccination compared with similar individuals at 22 to 42 days after vaccination,” according to the authors. Events such as strokes happen independent of vaccination. Therefore, the lack of statistically significant upticks implies that vaccination lacks the severe side effects researched. Certainly, mild side effects such as soreness, tiredness, and temporary fevers are common and acknowledged. But the new study suggests the vaccines are even safer than previously documented.

As with any scientific study, there are limitations to the findings. The statistical analysis may be tweaked in the future for greater accuracy, or other health impacts may be added for consideration. Further research will continue to illuminate the picture, but so far the data pointing to the exceptional safety of mRNA vaccines continues to accumulate. As America passes the grim benchmark of 700,000 deaths from COVID-19, the vaccine remains the most effective way to protect yourself against COVID-19 while also helping to protect your community. For more information on the vaccines and how to get your shot, check out

A large-scale study found that the mRNA vaccines Modern and Pfizer did not cause any immediate severe side effects across 6.2 million individuals.


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h/t: [IFL Science]

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Madeleine Muzdakis

Madeleine Muzdakis is a Contributing Writer at My Modern Met and a historian of early modern Britain & the Atlantic world. She holds a BA in History and Mathematics from Brown University and an MA in European & Russian Studies from Yale University. Madeleine has worked in archives and museums for years with a particular focus on photography and arts education. When she isn’t writing, she enjoys hiking, film photography, and studying law while cuddling with her cat Georgia.
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