People who’ve received the third dose of a Covid-19 vaccine are reporting rates of side effects similar to those after the second dose, according to data released Tuesday by the Centers for Disease Control and Prevention.
The new report, published in the Morbidity and Mortality Weekly Report, relies on submissions from thousands of people who received third shots of the mRNA vaccines from Pfizer-BioNTech and Moderna after such doses were authorized for people with compromised immune systems. People submitted their reactions to v-safe, the CDC’s smartphone-based surveillance network.
Among more than 12,500 people who completed surveys after each shot, 79.4% of people reported local reactions (including itching, pain, or redness at the injection site), while 74.1% reported systemic reactions (mostly fatigue, muscle aches, and headaches), typically the day after the shot. That compared to 77.6% and 76.5% of the people who reported local or systemic reactions, respectively, after their second shot.
Overall, among more than 22,000 v-safe registrants who’ve received third doses, “no unexpected patterns of adverse reactions were observed,” the report says. As of Sept. 19, some 2.2 million people in the United States had received additional doses of the Covid-19 vaccines.
The report focuses on the more common, less worrisome side effects of the mRNA vaccines, and doesn’t mention the very rare, but more serious events like anaphylaxis. Some vaccine side effects occur so infrequently that even studies of thousands of people don’t detect them; it’s only after the shots are administered into millions of arms that a connection becomes clear.
But the new data provide at least an early hint that in terms of immediate reactions, it doesn’t seem as if third shots cause more of a kick than the second shots did. Gathering such data is important as the government authorizes boosters for wider populations. Last week, the CDC recommended boosters for people 65 and older, adults with certain underlying health issues and those who workplaces or living sites place them at higher risk of coronavirus exposure. So far, those recommendations only apply for people who received the Pfizer vaccine as their initial series, but boosters for the Moderna and Johnson & Johnson shots are expected to eventually be authorized.
“These initial findings indicate no unexpected patterns of adverse reactions after an additional dose of Covid-19 vaccines; most of these adverse reactions were mild or moderate,” the authors wrote in the new report.
The authors note that enrollment in v-safe is voluntary and is “likely not representative of the vaccinated U.S. population,” with the majority of participants identifying as white.
Overall, the Covid-19 vaccines have proven to be remarkably safe as well as effective, and generally, experts don’t anticipate a significant increase in the likelihood of most side effects with booster shots. But there is some concern in particular with third doses of the mRNA vaccines and myocarditis and pericarditis, two types of heart inflammation that have appeared at the highest rates among boys and young men soon after the second shot. The worry is that a third shot could carry even higher risk — though for now, that’s just a concern — for that population, which in general remains very well protected by two doses of the vaccine. It’s led to a debate about whether third shots will be justified at some point for young men and boys broadly.
The Covid-19 vaccine booster shot’s side effects appear to largely mirror how people felt after their second dose, according to a study published Tuesday by the Centers for Disease Control and Prevention.
The report found that the side effects were mostly considered mild or moderate, and arm pain, fatigue and headache were the most commonly reported symptoms after the third shot.
The side effects kicked in generally the day after the injection, the report found, and 28 percent of people said they were unable to perform normal daily activities because of them.
Nearly 2.8 million people in the United States have received a booster shot since mid-August, when additional doses of the mRNA vaccines, both from Pfizer-BioNTech and Moderna, were first authorized for people with compromised immune systems.
Last week, a booster shot was recommended for an even larger segment of the population: People originally inoculated with the Pfizer vaccine either ages 65 or older or at higher risk of Covid due to underlying conditions or their occupation.
The new report looked at data from 22,191 people who received a booster dose and responded to questions on a CDC-run smartphone app called v-safe.
The vast majority of respondents reported initially getting the Pfizer or the Moderna vaccine, and nearly all got the same booster vaccine as their initial vaccine.
Arm pain was slightly more common after the third shot than the second, the report found, and systemic reactions, such as headache or fatigue, were slightly less common after the third shot compared with the second.
“This latest report includes some of the data of our early experience with third doses,” CDC Director Dr. Rochelle Walensky said Tuesday during a White House Covid task force briefing.
“The frequency and types of side effects were similar to those seen after the second vaccine doses, and were mostly mild or moderate and short-lived,” she added.
Dr. Helen Keipp Talbot, an associate professor of medicine at Vanderbilt University Medical Center in Nashville, said she was not surprised by the apparent safety of the third dose.
Talbot is a member of the CDC’s independent panel, called the Advisory Committee on Immunization Practices, which convened last week to discuss a Pfizer booster dose. She noted the group had seen and discussed the newly published data during its two-day meeting.
“We are very comfortable with the safety of these vaccines. They’ve been given to millions and millions and millions and millions of people,” she said.
“But that doesn’t mean we’re going to stop monitoring and stop looking” for adverse events, she said. “We’re always going to be cautious and careful.”