What Are The Side Effects Of The Coronavirus Vaccine?

Here's how you might expect to feel after getting the COVID-19 shots and how long issues such as fever or injection pain may last.

We now have a COVID-19 vaccine. And, like most, there will probably be mild to moderate side effects.

But many experts believe the benefits of getting immunized far outweigh potential issues if it means people are protected against the coronavirus.

“That is really critical for the general population — keeping people healthy so that they can go back to work, go back to school and so we can really reopen society in a way that we would like to,” said Yvonne Maldonado, a pediatric infectious disease epidemiologist at Stanford University.

So how exactly might it feel when you get the shots? Below, experts share some side effects that people may experience after receiving their COVID-19 vaccine.

Short-term side effects can include injection site pain, headaches and fever.

There are a number of COVID-19 vaccine candidates, but at this point, experts know the most about the Pfizer and Moderna vaccines.

“The safety of these vaccines is studied in a very rigorous way, through phase one trials, phase two and, most recently, in large phase three trials where tens of thousands of study participants received these vaccines,” said William Moss, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health.

The short-term side effects that some people experienced during the vaccine trials are in line with what is normally seen following a routine vaccination, Moss said, and these issues appeared in only about 5% to 15% of participants.

“What we know is individuals who receive these vaccines have inflammation ― the technical term for this is reactogenicity and this represents the body’s immune system response to the vaccine,” he said.

Post-vaccine side effects can include soreness at the site of injection, a low-grade fever, headaches, muscle aches and fatigue, Moss said. These effects can last around 12 to 36 hours after injection.

The side effects after the second vaccine dose are likely stronger than after the first dose.

The Pfizer and Moderna vaccine candidates both require two doses, meaning you’ll need two shots over a short period of time to be protected. In both of their trials, there seemed to be more of a reaction after the second dose, but side effects remained mild to moderate in about 90% to 95% of cases, Maldonado said.

“In some of the studies from Moderna, about one-third of people had a fever after the second dose, and they didn’t after the first,” Maldonado said, adding that people also reported higher rates of headaches and general aches and pains after the second dose.

These findings seem to be holding up, at least anecdotally, according to many people who have received the vaccine so far.

With the Pfizer vaccine, there was also an increased rate of headache, fever and aches and pains after the second dose during trials. But Maldonado stressed that the reported side effects were largely mild to moderate.

In more severe cases, she said physical responses such as a fever or bad headaches could keep people out of work for a day, but that has not been common so far.

Post-vaccine side effects can include soreness at the site of injection, a low-grade fever, headaches, muscle aches and fatigue, according to William Moss, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health. These effects can last around 12 to 36 hours after injection.
Post-vaccine side effects can include soreness at the site of injection, a low-grade fever, headaches, muscle aches and fatigue, according to William Moss, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health. These effects can last around 12 to 36 hours after injection.

There have been reports of some experiencing swollen lymph nodes after getting the vaccine.

The Society of Breast Imaging, a breast imaging organization, put out a notice in February that recommended women wait four weeks to schedule a mammogram following their COVID-19 shots. This is because the body’s reaction to the shot may mimic some signs of breast cancer, like swollen or a lump in the lymph nodes under the armpits.

This isn’t super common, but it has been reported in some patients who received both the Moderna and the Pfizer vaccines, Health reported. It likely occurs because your lymph nodes are connected with your immune system. And this reaction isn’t necessarily a bad thing; it’s a sign your immune system is responding to the vaccine. Experts say you can expect this side effect to last around a week or so, but the exact timing of when it’ll clear up likely varies from person to person.

The long-term side effects still have to be studied.

The accelerated development of these vaccines and the relative newness of the coronavirus make it impossible to study long-term side effects in the present moment.

“We know about short-term side effects, and the vast majority of side effects following vaccination occur within the first 30 to 40 days,” Moss said.

The current vaccine trial participants have passed this timeline.

“There is at least a two-month follow-up in at least half of the participants. So we know a lot about the short-term side effects of these vaccines,” he said.

But understanding the long-term side effects will require additional follow-up in the months to come.

Remember that side effects are not bad — they are an expected immune response.

There is no reason for alarm if you experience any of the anticipated side effects. It’s actually a good thing ― it means your body is responding to the injections.

“Most vaccines will have some degree of minor side effects. It is, in fact, the body’s immune and inflammatory response to the vaccine,” which is supposed to happen, Maldonado said.

The nature of an immune response will involve some degree of inflammation, whether that means redness, pain at the site of injection, swelling, headaches or a low-grade fever, she said.

Moss added that side effects can be treated in part with anti-inflammatory drugs, such as Advil or Aleve. Ultimately, the benefits of taking a COVID-19 vaccine should outweigh the discomfort.

Experts are still learning about COVID-19. The information in this story is what was known or available as of publication, but guidance can change as scientists discover more about the virus. Please check the Centers for Disease Control and Prevention for the most updated recommendations.