Rest assured: They are not expected to be much different from what you may have experienced with previous doses of vaccines and boosters. “We just don’t have data on that [yet]essentially giving two vaccines in one vaccine — but biologically, I simply wouldn’t expect the side effects, severity, or safety profile of the vaccines to be any different than current vaccines and mRNA boosters,” said Dr. Paul Offit, director of The Center for Vaccine Education at the Children’s Hospital of Philadelphia and a member of an independent advisory panel to the US Food and Drug Administration, tells CNBC Make It. The reformulated shots from Pfizer and Moderna are bivalent, meaning they target both the original Covid strain and omicron’s BA.5 and BA.4 subvariants. Adverse effect data are not yet available because the new boosters were approved by the FDA and the Centers for Disease Control and Prevention before their clinical trials were fully completed. The feds based their approvals on a lot of other safety evidence, including evidence from the original Covid vaccines — the updated formulations are just an adaptation of those originals — and the lab data on the BA.5 element of the mouse shots. They also reviewed clinical trial data on earlier versions of bivalent enhancers targeting the BA.1 subvariant of omicron. These shots were never released to the public because the BA.1 was quickly overtaken by other omicron subvariants — but their design is remarkably similar to the shots now available in pharmacies and clinics across the country. Together, the data shows a potential roadmap for the side effects you can expect after taking one of the new boosters, and how severe those side effects can be.
The expected side effects
In the Pfizer and Moderna clinical trials of the BA.1 vaccines, participants who were already fully vaccinated with a booster received an updated booster dose. In both clinical trials, the most commonly reported side effects within seven days of receiving the vaccine were:
Pain Fatigue Headache Muscle pain Chills Joint pain Redness and swelling at the injection site Fever
This is a familiar list: It’s the same group of side effects that come with the original formulations. But mostly, in these clinical trials, the severity of the side effects was very mild. The Pfizer trial found that about 52% of participants who received the BA.1 vaccine experienced mild pain at the injection site, 8% experienced moderate pain and only 0.3% experienced severe pain. About 26% of participants experienced a mild or moderate headache, while only 0.3% experienced a severe one. Moderna’s trial found that nearly 59 percent of participants experienced fatigue, but only about 4 percent experienced it at a Grade 3 level, which is defined as significant fatigue that interferes with daily activity. Serious side effects are “generally” more common after receiving a second vaccine dose, not after receiving a third or fourth dose, Offit says. You’re only eligible for the new boosters if you’ve completed a series of primary vaccinations, which means most people will have already had at least two doses earlier. The same idea applied to the final round of booster shots. The new vaccines have the same dosage amounts as the original vaccines, further suggesting that their safety profiles could be similar, Offit says. A single dose of Pfizer’s monovalent vaccine contains 30 micrograms of mRNA that targets the original Covid strain. The updated booster shots contain the same number of micrograms, with 15 targeting the original strain and the other 15 targeting BA.4 and BA.5. Moderna’s monovalent vaccine contains 50 micrograms of mRNA per dose that targets the original strain. Its updated booster has 25 micrograms targeting the original strain and 25 micrograms targeting the omicron subvariants. The BA.1 trials looked at only a few hundred people, which is a relatively small sample size compared to the thousands of Americans who are set to receive the new BA.5 doses, Offit notes. You can still be confident going in, he says — just don’t be 100 percent sure what to expect. “We should keep our eyes open for side effects and adverse reactions that may occur and keep in mind that this is a new product,” Offit says. Subscribe Now: Get smarter about your money and your career with our weekly newsletter Dont miss:
