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All vaccines come with potential side effects, though most are minor or uncommon. If you’ve ever felt arm tenderness after a flu shot or experienced a slight headache or fever, you’re familiar with such reactions. The new coronavirus vaccines may also cause side effects, possibly more pronounced, but this isn’t necessarily a cause for concern.
While no COVID-19 vaccine has been approved in the U.S. yet, progress is being made. The Pfizer/BioNTech vaccine, a leading candidate, recently received emergency authorization in the U.K. and may gain similar approval in the U.S. soon. Moderna’s vaccine is also under FDA review and could be approved this month. (The FDA will evaluate safety and efficacy data before making a decision. Approval isn’t guaranteed, but current data is promising.)
Fever and muscle aches are likely to be frequent side effects
Manufacturers of the leading vaccine candidates have indicated that side effects are generally mild to moderate, suggesting they do not present significant safety concerns. However, even mild or moderate reactions can still cause discomfort.
The Pfizer vaccine’s UK label lists very common side effects, each affecting over 10% of recipients: injection site pain, fatigue, headaches, muscle pain, joint pain, chills, and fever. (It’s important to note that experiencing all of these is not typical, but each one individually is common.)
Approximately 1 in 10 individuals may experience redness or swelling at the injection site, or nausea. In rarer cases, people have reported swollen lymph nodes and a general sense of feeling unwell.
To better understand these effects, consider reports from trial participants. One volunteer, unsure if she received the vaccine or a placebo, shared with MarketWatch that her arm was sore after the injection, leading her to believe she got the real vaccine. She described feeling sluggish, tired, and achy the next day. After her second dose, she experienced similar symptoms, including soreness, redness at the injection site, body aches, and fatigue.
During a recent CDC advisory committee meeting, experts emphasized the importance of public awareness about potential side effects. For instance, individuals might need to take a day off work if they feel unwell. Hospitals and essential businesses should plan accordingly, avoiding vaccinating entire teams, such as ICU staff, simultaneously.
Side effects indicate the vaccine is effective
Although these symptoms can be bothersome, they are not a cause for concern. Vaccines function by stimulating our immune systems to respond to a simulated threat. Symptoms like fever, fatigue, and muscle pain are natural reactions to infection, and a milder version of this response often occurs after vaccination.
Given the severity of COVID-19, the temporary discomfort of these side effects is a small price to pay for the significant protection against severe illness. However, if the vaccine is approved and you choose to receive it, it’s crucial to be informed about the potential reactions.
Public health officials are concerned that individuals who experience fever or fatigue after the first dose may be reluctant to return for the second. This is critical because most vaccine candidates require two doses for full efficacy. The Pfizer vaccine’s UK label emphasizes that full protection is not achieved until seven days after the second dose. With doses spaced at least three weeks apart, full protection begins approximately one month after the initial shot.
More details about the vaccines and their side effects are expected around the time of the FDA meetings—December 10 for Pfizer and December 17 for Moderna. Stay updated for further information.
