COVID-19 vaccine side effects causing worry for some people

Q: I am 53 and have diabetes. I live in California and can get the COVID-19 vaccination soon. What side effects can I expect? There are so many stories floating around, and knowing what to believe is hard.

A: It's true there's a lot of confusion and, sadly, misinformation about the coronavirus vaccine. We've been answering specific questions in recent columns, and we are happy to share the bigger picture with you and the rest of our readers.

At this time, three vaccines have received emergency authorization from the U.S. Food and Drug Administration. They are manufactured by Pfizer, Moderna and, most recently, Johnson & Johnson. Clinical trials found all three vaccines to be effective in preventing symptomatic COVID-19. The Pfizer and Moderna vaccines require two doses, with the second dose administered three or more weeks after the first. The exact interval depends on which vaccine you receive; you get directions about how and when to get your second dose at the time you receive your first. Johnson & Johnson's is a single-dose vaccine.

Potential side effects from the coronavirus vaccine can range from mild to severe. Anaphylaxis, which is a life-threatening allergic reaction, has received a lot of attention. However, this response to the vaccine is exceedingly rare. According to the latest figures from the Centers for Disease Control and Prevention, which tracks a wide range of data related to the vaccine, we are currently seeing about 2.5 episodes of anaphylaxis for every million doses of COVID-19 vaccine doses administered.

The vaccine itself is delivered via a very thin needle. Many people say they don't even feel the injection. After you receive the vaccine, you will be directed to a designated area to wait during the CDC-mandated 15-minute period before leaving the site. People at risk of an allergic reaction, which is determined via a pre-vaccination questionnaire, are asked to wait for at least 30 minutes. Each vaccine site is required to have on hand the medication, equipment and trained medical personnel needed to address potential serious allergic reactions.

Some people are having a stronger response to the second shot of the two-dose vaccines. Stock Photo

The most common side effect of the vaccine is temporary soreness and swelling at the injection site. This can begin anywhere from a few minutes to a few hours after the injection. Additional reactions can include fever, chills, headache, muscle aches, nausea and fatigue. These arise because the vaccine delivers a fragment of the coronavirus's genetic code to stimulate the immune system to recognize it as a foreign invader and mount a response. You can reduce potential discomfort at the injection site by exercising your arm prior to getting the vaccine, and by applying a cool, wet cloth to the injection site.

Some people have a stronger response to the second shot of the two-dose vaccines. If that's the case, over-the-counter meds such as aspirin, acetaminophen or ibuprofen can help manage post-vaccination symptoms. But don't take these meds ahead of time to prevent side effects, as it's not yet known if they affect the vaccine's efficacy. If symptoms don't go away after a few days, or if they grow worse, be sure to see your health care provider.

More COVID questions:

A reader shared that she is using an over-the-counter nasal antiseptic so that she will be less likely to spread the coronavirus should she become infected. “I read that killing germs in the nose can reduce your risk of bacterial infections such as MRSA and staph,” she wrote. “And some experts believe it can help fight COVID-19.”

It's true some patients use an antiseptic nasal spray to “decolonize” the bacterium Methicillin-resistant Staphylococcus aureus, also known as MRSA. However, these nasal sprays target bacteria, and not viruses. It's a crucial distinction, because COVID-19 is caused by a virus, and it doesn't respond to antibacterials. We're not familiar with data supporting this practice for COVID-19, and we would not recommend it to our patients.

 A reader who tested positive for COVID-19 in August asked about antibodies and immunity. “Do I need to get tested for antibody levels?” she wrote. “Should I get the vaccine? When will my immunity run out?” At this time, it's believed that antibodies persist for about 90 days after COVID-19 infection. The degree of immunity that they confer is not yet known, so the only reason to get the test would be out of curiosity. And, yes, we recommend everyone get the vaccine. This includes those who have tested positive for the coronavirus in the past and don't currently have COVID-19 symptoms.

 A reader wondered whether the anti-inflammatory she takes for a type of arthritis known as pseudogout presents a problem regarding the vaccine. “Does it affect the efficacy of the COVID-19 vaccine?” she asked. “Is one vaccine manufacturer better than another?” We are not aware of any data about decreased efficacy of the vaccine in individuals using either NSAIDs (nonsteroidal anti-inflammatories) or steroids. As for the vaccines, they are equally effective. We strongly recommend that our patients get the first one available to them.

 We heard from a number of readers asking if the vaccine is safe for people with disorders such as multiple sclerosis and Parkinson's disease. Both the Parkinson's Foundation and the National MS Foundation convened panels of experts to research this question. Their conclusions are that, yes, individuals with these diseases should get vaccinated. It's important to note that these recommendations apply only to the Pfizer and Moderna mRNA vaccines.

 A reader with Type O blood, which has been linked to a lower risk of serious illness with COVID-19, wondered about her need for a vaccine. “Do I need to get the vaccine since I have a low risk of getting COVID-19? If so, which one is best for me to get?” Yes, we recommend that our patients with Type O blood get vaccinated with either the Moderna or Pfizer vaccine, whichever is available.

 Many of you are wondering if blood thinners, both prescription and over-the-counter, affect the coronavirus vaccine's efficacy, and vice versa. It's a question we're getting from our own patients. The guidance at this time is to continue with blood thinners as prescribed, and to tell the person administering the vaccine that you are using them.

Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to

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