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 bodys 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 youll 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 didnt 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.