The anecdotal reports are true: people getting the Modern COVID-19 vaccine say they have more side effects than people getting the Pfizer / BioNTech shots, according to new data released this week in JAMA.
The study analyzed reports collected through a Centers for Disease Control and Prevention program called v-safe. It is an SMS-based application designed to detect side effects from vaccines. The first week after each dose of the vaccine, enrolling people are asked to complete a daily survey of any symptoms, such as fatigue or arm pain.
More than 3,600,000 people who received their first dose of COVID-19 vaccine before February 21 have signed up at v-safe and booked at least once. About 70 percent of people said they had a reaction at the injection site, such as pain or swelling, and half had a more common reaction such as fatigue or chills. For both, people who received a Moderna shot were more likely to have a side effect – 73 percent had a reaction at the injection site, compared to 65 percent of those who received a dose of Pfizer / BioNTech has. About 51 percent of Moderna recipients had symptoms of the body, compared with 48 percent of those who received Pfizer / BioNTech.
The gap widened after the second dose. About 1.4 million people completed the sign-ups. Nearly 82 percent of people who received their second Moderna shot have pain at the injection site, compared to just under 69 percent of those with Pfizer / BioNTech. Overall, 74 percent of people said they had general reactions to their Moderna shot, compared to 64 percent of people who received Pfizer / BioNTech. The biggest difference was for cold fever, which was experienced by 40 percent of the people taking Moderna and only 22 percent of the people taking the Pfizer / BioNTech survey.
People over 65 are also less likely to have side effects than people under 65, regardless of which vaccine they received.
The study did not include information on the severity of the side effects, so it is not clear whether one vaccine causes more disruptive effects than the other. In addition, the people who use v-safe may not be a representative example of people who get shots. Only about 10 percent of people enrolled in the program after being vaccinated.
In general, the side effects and frequency of side effects were similar to those seen in clinical trials testing these vaccines. The clinical trials gave researchers and doctors a close look at the types of side effects people can expect after being shot.
Anyone who gets a COVID-19 vaccine can sign up for v-safe here.
Correction 7 April, 13:20 ET: V-safe do collects serious information, although not reported in the report JAMA study. An earlier version of this story incorrectly stated that v-safe did not collect this information. We regret the mistake.