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Doctors & Advice, Family Health

What Is It Like To Get a COVID-19 Vaccination?

BY KATHY KATELLA February 10, 2021

Five things to know while you're rolling up your sleeve.

The COVID-19 vaccines are here. Two vaccines, one developed by Pfizer-BioNTech and one by Moderna, were each found to be approximately 95% effective in clinical trials and given Early Use Authorization (EUA) by the Food and Drug Administration (FDA) in December 2020. It’s expected that several other vaccines will become available as well. Depending on your age, occupation, and health status, you may be able to get your vaccination now—or it may be in a few weeks or months.

So, the question remains: What is it like to get a COVID-19 vaccine? Will it hurt?

“These COVID vaccines are no different than any other vaccine you might get—and that includes the annual flu shot,” says Onyema Ogbuagu, MBBCh, a Yale Medicine infectious diseases specialist and Yale’s leading expert on these COVID-19 vaccines. Like the flu shot, the COVID-19 vaccine involves a needle injection, sometimes described as a small pinch in the arm. “The recipient gets a small-volume vaccine, so not a lot of fluid goes in.”

We made a list of top concerns, and asked Dr. Ogbuagu to share insights. (He is the principal investigator of the Pfizer-BioNTech COVID-19 vaccine clinical trial supported by the Yale Center for Clinical Investigation at Yale School of Medicine, in partnership with the Yale New Haven Health System.)

If you have questions about what else to expect as you anticipate your vaccination, here are five things to know.

1. You may have side effects, but not necessarily.

Side effects from the COVID-19 vaccine are not uncommon—and also not something to fear. “They will be mild for the majority of people,” Dr. Ogbuagu says. “I also think when we use the term ‘side effects,’ it makes it seem like they're really bad things. Technically, we refer to them as them reactogenicity. These are just symptoms that mean you are responding to the vaccine—your immune system is really kicking in protection for you.” If you experience side effects, they typically appear and go away within 48 hours.

A good thing to know, though, is that some people have reported side effects that feel like symptoms of the flu. You might have a fever or fatigue that could, in rare cases, impact your daily activities for a few days. The following is a list from the Centers for Disease Control and Prevention (CDC) of common side effects among people who get a COVID-19 vaccine.

At the injection site:

  • Pain
  • Swelling

Throughout the rest of the body:

  • Headache
  • Tiredness
  • Chills
  • Fever

Some people have complained about a feeling of heaviness in the arm where the injection was given, Dr. Ogbuagu says, noting that this could be related to injection technique and/or the vaccine itself. While most people find the side effects tolerable, he suggests talking to your doctor if redness or tenderness lasts more than 24 to 48 hours, or if side effects are worrisome or don’t go away after a few days.

These COVID vaccines are no different than any other vaccine you might get—and that includes the annual flu shot. Onyema Ogbuagu, MBBCh, a Yale Medicine infectious diseases specialist

When you get the vaccine, your provider will give you information about a CDC smartphone tool called v-safe. If you register for v-safe, it will follow up by sending you personalized health check-ins. If you report side effects, someone from the CDC may call to check on you. The CDC also uses v-safe to send a reminder when it’s time to get the second dose. V-safe registration is voluntary and if you sign up, you can opt out at any time.

2. Yes, you do need two shots.

Both the Pfizer-BioNTech and Moderna vaccines require you to take two shots for maximum protection. It will be important to know which vaccine you get, since they should both come from the same manufacturer and the time between shots varies.

You should get the second shot as close to the recommended timing as possible, even if the first one causes side effects. It’s also important to know that the two vaccines should not be mixed—so if your first dose is the Moderna vaccine, the second dose must be Moderna as well.

There has been some confusion recently as the CDC updated its vaccine recommendations in late January to allow second COVID-19 doses from a different manufacturer in "exceptional situations.” The agency also said people may receive a second dose up to six weeks after the first if it's not feasible to follow the recommended window.

According to a spokesperson for the CDC, the "intention is not to suggest people do anything different, but provide clinicians with flexibility for exceptional circumstances." Getting both shots is critical, says Dr. Ogbuagu, because the first shot is only about 50% effective when it starts to kick in, about 10 days after you get it. “The vaccine’s effectiveness increases to 95% after the second shot,” he says.

Another reason you need two shots is that scientists are still determining length and durability of the vaccine’s protection—that’s something they will be tracking, says Dr. Ogbuagu. “The second shot is the one that will probably improve the durability of the vaccine. We saw this in the data in our early-phase clinical trials,” he says. “Some people never achieved target antibody levels with one shot alone. So, the booster [second shot] is what's really needed to meet, or exceed, the target antibody levels.”

3. You can feel safe getting the vaccine.

There are routine processes and procedures in place in the U.S. to ensure the safety of any vaccine, and the rules didn’t change for the COVID-19 vaccine. The FDA’s decisions to approve these vaccinations via EUA were based on safety and efficacy data from large clinical trials testing them in a large number of people.

“For the mRNA vaccines, we started with data from around 74,000 people, from studies that were multi-national, across racial and ethnic lines, in and outside the U.S., including in South America, South Africa, and Europe,” says Dr. Ogbuagu, adding that he was one of the first to get the vaccine at Yale when it became available to health care providers. “I personally have observed almost 300 patients getting the vaccines, so I know the side effects. I want to reassure everyone that the vaccine is as safe and effective as it sounds.”

Dr. Ogbuagu, speaking during a press conference related to the COVID-19 vaccine rollout on Tuesday, Dec. 15, 2020, at Yale New Haven Hospital. Photo credit: ©Kristin Hynes/Yale New Haven Health


Some people have expressed concerns about how quickly these vaccines were developed—in less than a year. But both use a technology that researchers have been studying for decades against other infections, including the flu and Zika. Both are messenger RNA (mRNA) vaccines that use a technology that is very easy to mass produce. “The bottom line is that the clinical trials were done more efficiently than they would have been if we had more time. There were no shortcuts,” Dr. Ogbuagu says. “This is how clinical trials should be done in response to a public health emergency. COVID-19 galvanized pharmaceutical companies, academic institutions like ours at Yale, and researchers like me. It was a testament to how things can happen when we all work together.”

4. Allergic reactions are rare—and treatable.

You may have heard that some people have had severe allergic reactions to the vaccines, but Dr. Ogbuagu says that these reactions have been rare (estimated to be around 2/1,000,000 doses of Pfizer-BioNTech vaccine administered, per the CDC’s Vaccine Adverse Event Reporting System [VAERS]) and that this can happen with other vaccines and medications as well. “The vast majority of people have been fine,” he says. The term “severe allergic reaction” means that people who experience one need to be treated with epinephrine or an EpiPen©, or they have had to go to the hospital. There have also been some reports of non-severe reactions such as hives, swelling, and wheezing.

If you have a history of severe allergies to any vaccines or medications, you should discuss this with your doctor prior to getting the vaccination. Also, know that the CDC has recommended monitoring people for any reactions for at least 15 minutes after the vaccination—and for at least 30 minutes for those with a history of reactions.

Vaccination sites will have medication and equipment for treating reactions, and on-site providers know how to use them to provide rapid care, if needed. (The CDC advises anyone who has a severe allergic reaction to the first dose of an mRNA vaccination to not get a second dose.)

More information about severe allergic reactions is available on the CDC website. If you think you might be having a severe allergic reaction after leaving the vaccination site, call 911 for immediate medical care. 

5. Yes, you should keep social distancing and wearing a mask after vaccination.

“I don't think we're ready to tell people to throw away their masks or avoid social distancing quite yet,” Dr. Ogbuagu says. “We know that the masks work to keep you from spreading COVID-19 to others, and we now know that it protects you from acquiring it, too.”

Similar to the flu shot, it's always technically possible to become infected with COVID-19 even if you get the vaccine. While the Pfizer-BioNTech and Moderna vaccines are deemed to be 95% effective, that leaves about 5% of people who may get the virus even though they were vaccinated. Even if their case is mild or they don’t have symptoms, they could still spread the virus to others, as could people who have not yet been vaccinated or whose immunity hasn’t yet built up from the vaccine, as it takes some time.

“But the good news is, as more of us get vaccinated, the odds any of us will get sick go down and—with these vaccines—we can start to envision a day when COVID-19 is no longer dominating our lives,” says Dr. Ogbuagu.

While the CDC makes recommendations for who should get the COVID-19 vaccine, each state has its own plan for deciding who will be vaccinated first.  Contact your state or local health department  for more information on when you will be eligible for the vaccine and where to get it in your area. Connecticut residents can find information here .

[Visit Yale Medicine's Vaccine Content Center for more stories on COVID-19 vaccines.]