What to Expect After Getting a COVID-19 Vaccine

The big question of the past year was when COVID-19 vaccines would become available. Now, the shots are finally here in the U.S.—albeit not without some significant distribution issues—and making it into more arms each day as state eligibility requirements expand to include groups like elderly adults, first responders, restaurant employees and teachers, in addition to health care workers and nursing home residents.

So, for many, the question is now what to expect after getting vaccinated. Here’s what to know.

What will the side effects be like?

So far, there are three COVID-19 vaccines authorized for use in the U.S.: those made by Pfizer-BioNTech, Moderna and Janssen/Johnson & Johnson. They share many of the same common side effects, including swelling and/or redness at the injection site, fatigue, headache, muscle pain, chills, joint pain and fever. Some people won’t experience anything worse than a sore arm, and for most people who do have side effects, they are fairly mild. But some people have reported feeling pretty lousy—almost as if they had the flu for a day or two.

Side effects tend to be worse after the second dose of a Moderna or Pfizer-BioNTech vaccine, so you may want to take a day off from work or school after getting your second shot. According to U.S. Centers for Disease Control and Prevention (CDC) data from January, after the second dose of the Pfizer-BioNTech shot, about 75% of people experienced pain, half experienced fatigue and about 42% experienced headache or muscle aches. Chills, fever, swelling, joint pain and nausea were less common. (The report didn’t include data about the second Moderna dose, but reactions are likely to be similar.)

The vaccines do not contain live virus, so they do not actually infect you with COVID-19; the side effects are a sign that your immune system is responding to the vaccine, says Angela Shen, a visiting scientist at Children’s Hospital of Philadelphia’s Vaccine Education Center. (But don’t worry: if you don’t get side effects, that doesn’t mean your vaccine isn’t working.)

To relieve side effects, Shen recommends applying a wet washcloth to the injection site, drinking plenty of fluids and wearing loose clothing. You can take over-the-counter pain medication if you must, but it’s better not to, Shen says. (More on that below.)

Should I avoid painkillers before getting vaccinated?

To play it safe, don’t premedicate. Some studies, both on the virus that causes COVID-19 and other viruses, have suggested that painkillers like ibuprofen (Advil) may interfere with the body’s ability to mount an immune response against the pathogens. For that reason, Shen recommends skipping painkillers prior to vaccination, unless you need them to manage another medical condition. It’s not such a big deal to pop one after your shot, but if your side effects are mild enough that you don’t need to, err on the side of avoidance, she says.

How long will I need to be monitored for an allergic reaction?

Very few people have experienced allergic reactions after receiving COVID-19 vaccines—about 11 people per million doses of the Pfizer-BioNTech shot and about 2.5 people per million doses of the Moderna shot, according to CDC data. Most of those people had previously experienced severe allergic reactions. Most showed signs of anaphylaxis within 15 minutes of getting the vaccine, so the threat seems to be mainly a short-term one.

Most vaccine sites have designated monitoring areas to watch for allergic reactions. If you have a history of allergic reactions, Shen recommends staying for 30 minutes, as opposed to the standard 15. After that, you’re probably out of the woods—but if you do experience a reaction later, be sure to report it to your doctor and seek medical care if necessary.

Can I drink alcohol after getting vaccinated?

Some European health experts have recommended that people avoid drinking a few days before and after their shots, apparently to avoid taxing the immune system. It’s true that alcohol use can suppress immune function over time, but neither the CDC nor vaccine makers specifically advise people against drinking around the time of vaccination. Clinical trial participants were also not asked to avoid alcohol during testing.

“There’s no evidence to say you should abstain,” Shen says, but it’s not a bad idea to do so anyway as a precautionary measure. There are plenty of reasons not to drink alcohol, and it can be helpful to give your body time to adjust after getting a vaccine, she says.

When am I fully protected?

The CDC considers someone “fully vaccinated” two weeks after receiving their final vaccine dose—the second shot of a Pfizer-BioNTech or Moderna regimen, or the single Johnson & Johnson shot.

What will be safe after I get vaccinated?

All of the COVID-19 vaccines authorized in the U.S. are very good at protecting their recipient from symptomatic disease.

What remains to be seen is whether a vaccinated person can still become infected with the virus (without developing symptoms) and then spread it to others. Promising preliminary evidence suggests the shots reduce transmission somewhat—the question is, by how much? That’s why experts are urging people to continue wearing masks and social distancing even after getting vaccinated.

That’s also why there’s no easy answer as to what will be safe after you get vaccinated. While you, personally, would likely be protected from COVID-19 if you took a trip or went to the movies, it’s not yet clear whether you could be unknowingly contributing to community spread.

After you’ve been fully vaccinated, the CDC says you can spend time in a private home with other fully vaccinated people, mask-free. You can also visit a household of unvaccinated people, as long as none of them have underlying health conditions that put them at risk for severe disease. In public, however, you should continue to wear a mask and avoid crowds, even if you’re vaccinated.

Will I need a booster shot in the future?

It’s possible, but doctors don’t know for sure how long immunity will last. In January, Moderna’s CEO estimated his company’s shot may confer immunity for a couple years, so it’s reasonable to assume you’d need a booster in a few years’ time, if COVID-19 is still circulating at that point.

Viral variants may also necessitate booster shots. So far, existing COVID-19 vaccines have proven effective against new variants that have emerged as the virus mutates, but over time, it may mutate enough that scientists have to tweak the shots. Fortunately, both Pfizer-BioNTech and Moderna have said it would only take about six weeks to create new shots that incorporate the variants’ unique genetic material.

Write to Jamie Ducharme at jamie.ducharme@time.com.