Side effects are not unique to COVID-19 vaccine

Side effects from vaccines are not uncommon. The seasonal flu shot, for example, can cause fever and fatigue, among other reactions. And the vaccine to prevent shingles can induce shivering, muscle pain and an upset stomach, to name a few.

In some ways, these mild to moderate reactions are “a good thing,” Moss says, because “it’s a sign that the immune system is responding to the vaccine.” Nevertheless, they shouldn’t be downplayed. For some people, a sore arm “is a big deal,” Chen points out. Reactions from the coronavirus vaccine may even cause recipients to miss a day or two of work.

The key, experts say, is to weigh the temporary discomfort against the long-term benefits: a potentially high level of protection from a disease that has uprooted everyday life for many of us and has killed more than 1.6 million people globally.

“We are willing to tolerate discomfort in other aspects of our life — many people exercise and have muscle aches afterward, and don’t say, ‘I’m never going to exercise again,’ ” Moss points out. “There are just many aspects of our lives where we need to be willing to make the trade-off for some degree of discomfort for a longer-term gain.”

It’s also important to keep in mind that the majority of reactions occur shortly after vaccination, so “there is a degree of reassurance” that the side effects reported in the clinical trials are likely the extent of any unpleasant short-term reactions, El Sahly says.

Older adults could experience fewer side effects

An interesting finding from the Pfizer-BioNTech and Moderna clinical trials is that while the vaccines seem to be just as effective in older adult participants, people 65 and older experienced fewer side effects than younger volunteers.

Researchers are still studying why this is the case, but it could have something to do with the declining immune response that comes with age. Because the coronavirus vaccine can provoke “a little bit of an inflammatory response,” Chen says, it may be that older adults react less to the medicine if they have “a blunted immune response already.”

Reports of a few adverse events

Federal analyses of both vaccine trials show that few adverse events — which the CDC defines as any health problem that happens after a shot — separate from the less serious side effects were reported. Swollen lymph nodes (lymphadenopathy) occurred in a small portion of the participant population. And four people who received Pfizer’s vaccine and three who received Moderna’s developed Bell’s palsy, which, in most cases, causes temporary weakness or paralysis in the face.

FDA scientists have said that the documented cases of Bell’s palsy are “consistent with the expected background rate in the general population” and that “currently available information is insufficient to determine a causal relationship [between Bell’s palsy and] the vaccine.” However, the situation is worth monitoring, health experts say.

What’s more, since the start of Pfizer’s vaccine rollout, two people in Great Britain and one person in Alaska have experienced severe allergic reactions after being vaccinated. The FDA is warning health care providers not to administer the Pfizer-BioNTech vaccine to individuals with a known history of a severe allergic reaction to any component of the product.

It’s important to keep in mind that these reactions, though serious, are relatively rare, seeing how tens of thousands of people have been inoculated with one of the two vaccines. “It’s a warning for a very small number of people,” says Barry Bloom, professor of public health in the department of immunology and infectious diseases at Harvard’s T.H. Chan School of Public Health.

If you’re concerned that your allergies could trigger a severe reaction to a coronavirus vaccine, talk to your doctor. And consider getting your vaccine in a medical setting, in case you do react.

“Most people can get the vaccine at pharmacies or a variety of different places. For people who’ve had allergic reactions, it’s a reason why they should talk to their doctor first — they [may] want to go to a place that’s more equipped for serious allergic reaction,” Karyl Rattay, director of the Delaware Division of Public Health, said in a recent news conference.

Safety monitoring doesn’t stop when vaccines become available

Just because the vaccines have expanded from trial participants to the public doesn’t mean monitoring for them will stop. Individuals who receive the vaccines will continue to be watched for long-term side effects and adverse events or disease. This follow-up will also give researchers more information on how long immunity to COVID-19 lasts after vaccination.

Something else that won’t stop when the vaccines are rolled out: the recommendation that people continue the prevention efforts that can help slow the spread of the disease, including mask wearing, social distancing and frequent handwashing. That’s because it typically takes a few weeks for the body to build immunity to a disease after vaccination, according to the CDC, meaning it’s possible you can get sick with COVID-19 even after you’ve been vaccinated. Plus, experts still aren’t sure whether the vaccines, which are highly effective at preventing COVID-19, block transmission of the virus.

Finally, it takes time to build up what Chen calls “community immunity,” or herd immunity, where enough of the population is protected from the virus that transmission slows significantly. Experts are not sure what the magic number is to obtain herd immunity for COVID-19, but they estimate it’s somewhere around 70 percent of the population, which could take months to achieve through vaccination.

“And before that, I don’t think anyone can let their guard down,” El Sahly says.