What are the side effects?

Sore arms are common. Fatigue develops in about half the people who get the vaccine. Headaches, chills and muscle pain occur in about 25% to 33% of patients. Patients report a wide spectrum of responses, from no reaction at all to symptoms like uncontrolled shivering and “brain fog.” While these experiences aren’t pleasant, they are a good sign that your own immune system is mounting a potent response to the vaccine.

As vaccines go, experts have agreed, the two COVID vaccines being distributed now elicit more reactions than most. “We call them ‘side’ effects, but it’s really just an effect,” said Dr. Paul Offit, a member of the Food and Drug Administration’s vaccine advisory panel. “This is what your immune response does when it’s responding to an infection.”

When will side effects show up?

Side effects like fatigue, headaches and muscle pain should show up within one to three days after vaccination, and resolve one to three days after they start.

If I have allergies, should I be concerned about the vaccine?

Severe allergic reactions, called anaphylaxis, are rare, but they have occurred in the minutes following an injection with the new vaccines. The rate of anaphylaxis has been 11.1 cases per million doses, as of December. By comparison, the rate of severe allergic reaction to the flu shot is about 1.35 cases per million doses. All the patients who experienced severe reactions were treated and have recovered. If you’ve ever had anaphylaxis for any reason, talk to your doctor about what precautions to take.

Are side effects after the second shot worse than the first shot?

Yes. After the second shot, people have reported bad headaches, upset stomach, chills, itching, fatigue and symptoms that feel like a bad flu and send them to bed for a day. Many people are fine. But just in case, plan to schedule a day off from work to rest after the second dose.

Does taking a pain reliever blunt the vaccine’s effectiveness?

Most experts agree it’s safe to take a pain reliever or fever reducer like acetaminophen or ibuprofen to relieve discomfort after you get vaccinated. You shouldn’t try to stave off discomfort by taking a pain reliever before getting the shot. While fevers and aches are a sign that the body is mounting a strong immune response, a review of the research shows that antibody levels aren’t significantly different in patients who take pain relievers after getting the vaccine.

I got the vaccine but haven’t had side effects. Is it working?

Just as some people experience side effects from medications and some don’t, people have varied reactions to vaccines. While we tend to hear only about the unpleasant reactions after the vaccine, a lot of people experience only mild discomfort or no symptoms at all after getting the shot.

Is it true that cosmetic wrinkle fillers can react to the vaccine?

A rare side effect of the vaccine has occurred in a few people who have used dermal fillers, which are gel-like substances injected to smooth wrinkles and facial lines and plump lips. In a few cases, people have developed swelling in areas that had been treated with the fillers.

The American Society for Dermatologic Surgery said people with dermal fillers should not avoid the COVID vaccine. The side effect is rare, temporary and responds to treatment. The side effect has not been seen with wrinkle-relaxing injections like Botox or Dysport.

What if I’m allergic to eggs or other vaccine preservatives?

The Pfizer and Moderna vaccines don’t contain egg or any preservatives found in common vaccines. The vial stoppers are not made with natural rubber latex, so the vaccines are safe for people with latex allergy. As new COVID-19 vaccines come on the market, you should double-check ingredient lists if you have had allergic reactions in the past.

Is there a risk of developing COVID-19 from the new vaccines?

No. The Pfizer and Moderna vaccines do not contain any live virus, weakened virus, dead virus or any infectious element, so there is no way for the vaccine to give you COVID-19.

What type of problem should be reported as an adverse event?

Any serious health issue that requires medical treatment in the days or weeks following vaccination should be reported. But even less serious problems should be reported, too.

“I think people should report everything that they think might be related to the vaccine, no matter how bizarre or biologically implausible,” said Offit. “If enough people report something similar, then it would be worth investigating.”

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