Young children who get the Pfizer-BioNTech COVID-19 vaccine often have mild side effects, but serious reactions are rare, according to a recent government analysis on vaccine safety in children ages 5 to 11. The data come from the Vaccine Adverse Event Reporting System (VAERS), a large vaccine safety surveillance system maintained by the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA), and v-safe, the CDC’s smartphone-based reporting system specifically for COVID-19 vaccine reactions.
“After over 8 million COVID-19 vaccinations in this age group, we found that side effects reported to v-safe were generally very mild and included things like injection site pain, and fatigue and headache, and were mostly reported the day after vaccination,” says Anne Hause, the lead author of the CDC’s research. The report, released on on Dec. 31, 2021, included data gathered between Nov. 3 and Dec. 19.
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Of the reactions reported to VAERS, 97.6% were for non-serious side effects, and 2.4% were for serious reactions. Only 11 verified cases of myocarditis, or inflammation of the heart muscle, were reported, and all children had recovered or were recovering. Two deaths were reported to VAERS; both children were in “fragile health” before vaccination and had multiple chronic medical conditions, and the data do not suggest a causal link between death and vaccination, the report says. V-safe data revealed that though reactions to the shots were common, the vast majority were mild. Only 1% of parents sought medical care for their child in the week after vaccination.
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Because the latest report included information from two different surveillance systems—VAERS and v-safe—the results are particularly comprehensive. The two systems collect data differently. Any patient (or in the case of a child, their parent) can report an adverse reaction to any vaccination to VAERS. That ease of reporting means that the system can catch even a very rare adverse event or unusual pattern, but it can be difficult to determine what’s actually causing the adverse event or how often it’s really happening, especially because the system has a negative bias; adverse reactions are more likely to get reported to VAERS if they’re more serious, according to the FDA. News reports of side effects or controversies about vaccines can also skew how many people report a particular adverse reaction. “Everyone can dump anything into that database, and people in the past have for non-medical reasons,” says Saad Omer, director of the Yale Institute for Global Health. For instance, in research published in the Pediatric Infectious Disease Journal in 2020, Hause, Omer and other researchers found that after California eliminated non-medical vaccine exemptions in 2015, adverse reaction reports to VAERS rose. The researchers suspected that the increase was because parents were seeking medical exemptions for their children and thought that reporting to VAERS would make it easier to do so. It’s up to researchers to sort out how many of the reactions reported to VAERS are caused by the vaccine itself and aren’t just symptoms that coincidentally occurred after they’d received the shot; they do this by thoroughly investigating concerning cases, interviewing health care professionals and reviewing electronic health records.
People who join the other database, v-safe, are encouraged to report their child’s reactions as they occur. Simple questions are sent by text message in the following days, like how their child felt and whether they were able to go to school afterward. V-safe participants are also asked to contribute to other tracking services; if they approached a health care provider to receive care for their child, for example, they were encouraged to report what was happening to VAERS.
The Pfizer-BioNTech COVID-19 vaccine for children has been monitored especially closely ever since it was authorized under emergency use; it was approved for kids ages 5-11 in October 2021. (It was authorized for kids ages 12-15 in May 2021 and is fully FDA approved for people ages 16 and older.) That authorization status means that providers are required to report certain kinds of adverse events, says Dr. Tom Shimabukuro of the CDC’s COVID-19 Vaccine Task Force. “The COVID-19 vaccines have been monitored under the most intense monitoring process in the history of vaccination,” says Shimabukuro.
Neither database can tell scientists everything they need to know about the safety of COVID-19 vaccines in children. But they can show how the vaccines are affecting kids in real life—and what we know now is encouraging.
