More information about the COVID-19 vaccines


Dear Doctor: 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.

Dear Reader: 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.

Elizabeth Ko, MD and Eve Glazier, MD

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.

(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)