If you got the COVID vaccine but didn’t experience any side effects, is it still working?

Doctor administering vaccine into arm, what happens if you have no side effects from the COVID vaccine
Photo via Blake Patterson/Flickr (CC BY 2.0)

A number of well known side effects have been associated with the COVID-19 vaccines. Experts and physicians advise vaccine recipients to expect these side effects, as they are a sign the vaccine is working. But if you get the vaccine and don’t experience side effects, does that mean it isn’t working?

Infectious disease experts say there is no evidence to suggest a lack of side effects after receiving the COVID-19 vaccine indicates a person has less protection against the virus.

According to the CDC, common COVID-19 vaccine side effects include pain, redness, and swelling at the injection site, along with tiredness, headache, muscle pain, chills, fever, and nausea throughout the rest of your body. These symptoms can last for several days but should always be temporary. If they become concerning or they last for more than a few days, the CDC recommends consulting a doctor.

As noted by Thaddeus Stappenbeck, chairman of the Department of Inflammation and Immunity at Cleveland Clinic’s Lerner Research Institute, not everyone is expected to experience side effects. In fact, more than 50% of vaccine recipients in trials didn’t experience any side effects at all but still emerged from their second vaccination with 94% protection.

The reasoning behind why some people experience side effects and others do not has yet to be determined. According to Sarah Coles, a family physician and assistant professor at the University of Arizona College of Medicine, several factors may play into peoples’ reaction to the vaccine. These include their level of fatigue, pain tolerance, and stress levels. 

Experts say the vast majority of vaccine recipients can expect basic local side effects, including soreness at the injection site. More serious side effects, however, like fatigue, fever, and nausea occur in less than half of people. The far more severe anaphylaxis was only identified in 4.7 cases per 1 million doses administered for the Pfizer vaccine and 2.5 cases per 1 million doses for Moderna’s vaccine, according to data collected by the Journal of the American Medical Association.

No matter what side effects you experience—even if there are none—the vaccine is doing its job. 

Read more on the coronavirus vaccines:

Sources: CDC, MedicalXpress, Cleveland Clinic, JAMA

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