Why Do Some People Experience COVID-19 Vaccine Side Effects While Others Don’t? Experts Weigh in
Common symptoms should be manageable and subside on their own
If you’ve received the COVID-19 vaccine, you may have experienced common side effects such as pain, fatigue, or fever, or perhaps you didn’t experience any vaccine reactions at all.Even if you didn’t have any adverse reactions, you likely know someone who did. So, why do some people have COVID-19 vaccine reactions while others don’t? Keep reading to find out what our experts have to say.
Common COVID-19 vaccine side effects
“The most common side effects of COVID-19 vaccines are mild,” explains Jennifer Bourgeois, Pharm.D., SingleCare pharmacy and health expert. “These include injection site pain; swelling or redness (most common across all vaccines); fatigue; headache; muscle or joint pain; and fever or chills.”
Of course, there are multiple manufacturers and variations of COVID-19 vaccines, and adverse effects are relatively common with the mRNA vaccines (Pfizer and Moderna), as well as the Novavax vaccine. That’s according to Kiran Dintyala, M.D., CEO and president of Stress Free Revolution. Slightly higher reaction rates have been reported for the Moderna vaccine than for the Pfizer vaccine, highlighting mRNA vaccine side effects.
“In general, the rates of common reactions are lower among older people (over 65) compared with younger adults and are lower among younger children than adolescents,” says Dr. Dintyala.
As for why these reactions occur, Bourgeois says when you get any vaccine, it helps your body learn how to fight off the virus. Normally, when a virus gets into your body, your immune system has to figure out how to defeat it. The COVID vaccine immune response and, as such, the vaccine aftereffects gives your body a practice round, so it can learn how to fight the virus without you actually getting sick.
With that in mind, sometimes your body might feel tired or have a sore arm after the shot because your immune system is gearing up to protect you, she adds.
Why some people experience COVID-19 vaccine side effects
“While side effects can be a sign of an immune response, not experiencing them does not indicate that the vaccine is less effective,” affirms Bourgeois. “The body still produces an immune response, even in the absence of noticeable symptoms.”
People who do not experience side effects can still mount a robust immune response, she adds. Factors such as age, underlying health conditions, genetic disposition, and how your immune system responds to the COVID-19 vaccine can all influence whether or not you experience side effects. More specifically, many sources suggest that healthier individuals—especially young adults and females—are more likely to have side effects from the vaccine because of stronger immune reactions, offers Jennie Stanford, M.D., FAAFP, DipABOM, obesity medicine physician and medical contributor for Drugwatch.
How to manage COVID-19 vaccine side effects
While there is no way to completely prevent adverse reactions to vaccination, side effects should be manageable.
Managing COVID-19 vaccine side effects can be as simple as using pain relief medications like acetaminophen or ibuprofen to reduce pain, fever or body aches. Additionally, you should stay hydrated and rest after vaccination, especially if you experience fatigue or body aches. Applying a cool compress to the injection site can help reduce swelling or soreness, she adds.
When to see a doctor
While most COVID-19 vaccine reactions are mild to moderate, it’s important to consult a health care provider if you find your side effects worsening over time. In rare cases, more severe side effects may occur.
Common side effects usually resolve within one to three days after vaccination, says Bourgeois. Most symptoms like fever, chills, and fatigue should subside within 48 hours. However, she notes, localized pain or swelling at the injection site can persist for several days longer.
The following scenarios warrant prompt medical attention, says Bourgeois:
- Side effects persist for more than a few days or worsen over time.
- You experience severe allergic reactions, such as difficulty breathing, swelling of the face, or hives (these typically occur within the first few hours post-vaccination).
- You experience chest pain, shortness of breath, or severe leg swelling.
- Your fever reaches 104°F (40°C) or higher.
- You experience frozen shoulder or a change in arm mobility.
For more tips on managing COVID-19 vaccine side effects or if you have concerns about severe vaccine reactions, consult your healthcare provider for personalized advice.
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