As the novel coronavirus pandemic hit last winter, everyone had numerous questions and concerns: “How long will this last?” “Am I going to get sick?” “When will we have a vaccine?”

Now that the coronavirus vaccines are here, everyone has more questions: “Are they safe?” “Will they make me sick?” “How long will it last?”

To answer your questions, we tapped infectious disease researcher S. Wesley Long, M.D., Ph.D., a clinical pathologist and microbiologist and at Houston Methodist, and who has researched COVID-19 and the various new strains and sports medicine physician Kevin Bernstein, M.D, competitive cyclist, and chief medical officer for Peaks Coaching Group, who has researched the vaccines and created a webinar on COVID-19 vaccines for endurance athletes.

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Here’s what you need to know.

This is a rapidly developing situation. For the most up-to-date information, check resources like the Centers for Disease Control and Prevention (CDC) regularly. This story will be updated as new information becomes available.

Is it Safe to Get the COVID-19 Vaccine?

Yes. “We now have data from millions of people who have been vaccinated, and CDC data shows that severe allergic reactions are very, very rare,” Long says.

Specifically, the CDC’s latest report (released January 22, 2021) reports that more than 4 million people in the United States have received Moderna’s coronavirus vaccine and anaphylaxis—the most worrying potential allergic reaction, which can be life-threatening—occurred at a rate of 2.5 cases per 1 million shots. A CDC report on the Pfizer-BioNTech coronavirus vaccine from earlier this month reported that anaphylaxis occurred at a slightly higher, but still very rare rate of 11.1 per 1 million vaccines.

“These reactions are incredibly rare, and more common in people with a history of severe allergic reactions,” Long says. “Vaccination sites are monitoring people after the vaccine to make sure they don’t have a severe allergic reaction, which usually happens quickly after the shot.” The medical staff should be equipped to administer an epinephrine injection (similar to EpiPens for food and bee sting allergies) to anyone suspected of having a severe reaction.

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The biggest safety concern most people have is that the vaccine happened “so fast,” Long says because there’s an impression that it was put together in a year’s time. It’s actually more like 20-plus years, Long says.

“The mRNA technology (which is being used in the Pfizer-BioNTech and Moderna vaccines) has been around since the late 1990s. Scientists tried it for other viruses, with varying degrees of success. That experience helped refine and improve the technology. So the technology was already there. They just needed the virus to be sequenced, which happened in January, to start working on it for this coronavirus. All the money and resources that were poured into development because of the pandemic allowed it to move along very quickly. But this technology is not brand new,” Long says.

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If you’re immunocompromised, you can consult with your physician before getting vaccinated, but the CDC says that people with autoimmune disorders or who are otherwise immunocompromised can get the COVID-19 vaccine, provided they don’t have other reasons not to, such as a history of severe allergic reactions.

Can the Vaccine Make You Sick?

No. None of the approved vaccinations use a live virus. Any reactions you might experience are your immune system doing its job, Long says.

“Once you have a vaccine, your immune system mounts a response, which is really hard to predict and varies person to person,” he says. “Some people feel crummy for a day or two. You may have a low-grade fever. You may have some muscle soreness or fatigue. It might hurt where you got the shot. You might get a headache. All of that just means the vaccine is doing its job.”

Anecdotally, people seem more likely to feel these symptoms after the second, booster shoot, say both Bernstein and Long, likely because that’s when your body kicks its immunity into high gear to give it the boot. While the side-effects aren’t pleasant, they are better than getting COVID-19.

Importantly, if you don’t feel any side effects, that doesn’t mean the shot didn’t work. “You can have a good immune response to the vaccine without feeling bad,” Long says.

Will the Vaccine Change My DNA?

No. This question is circulating because the Pfizer and Moderna vaccines are mRNA vaccines.

“mRNA is the messenger that carries instructions from your DNA to other parts of the cell to make proteins. mRNA doesn’t get transcribed back into DNA and inserted into our genome in our cells. That’s not the natural flow of information,” Long says.

So in the case of these vaccines, scientists have produced a synthetic version of the mRNA that the virus uses to build its spike protein. You get that mRNA injected into your deltoid muscle and those muscle cells make the spike protein of the virus. Your immune cells recognize those cells have a spike protein and launch an immune system response to get rid of them, and to remember what that spike protein looks like for next time.

“It’s a very robust natural reaction that mimics what would happen with an actual infection,” Long says. “The nice thing about this vaccine is that it is very easy to make changes and to synthesize mRNA, so this type of vaccine is easy to adapt should we need to respond to a new variant down the road.”

The proteins never assemble to form an actual virus, so you can’t get sick with coronavirus from the shot, Bernstein explains. “If you think of the virus as a Mustang, the mRNA is the instruction booklet on making an emblem for the hood of the car,” he says. Your body recognizes the entire virus (or Mustang) from just that distinguishing part (the emblem) and makes the immunity tools it needs to dismantle it on sight.

So the vaccine is safe and will not alter your DNA in any way. As with all vaccines, you may experience some symptoms as your immune-system mounts a reaction. (See above for details of those reactions.)

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The Oxford-AstraZeneca vaccine and soon-to-be-released Johnson & Johnson vaccines are viral vector vaccines. That means the vaccine uses a safe, modified version of the virus (a.k.a. the vector), which in this case are the spike proteins found on the surface of the coronavirus. That vector is injected, and your body mounts an immune response, which it remembers should it encounter those spike proteins on the actual virus down the road. These don’t change your DNA either. Viral vector technology is also not new; it has been around since the 1970s.

Is the Vaccine Free?

The shot itself is covered by U.S. taxpayer dollars, so technically you’ve already paid for it, and yes, it is essentially free for all. That said, vaccine providers can charge an administration fee for giving the shot. That cost can be reimbursed by insurance. Uninsured people can get the cost covered by the Health Resources and Services Administration’s Provider Relief Fund. No one can be denied a vaccine if they are unable to pay.

How Long Does the Vaccine Last?

That’s to be determined, but so far the immune-system response appears to last, Long says. “The latest data is six months out and most people still have really good protection from the vaccination. We’ll know more as time goes on, and they continue to follow up with people from the clinical trials.”

Can I Ride After I Get the Vaccine?

Yep. “I did a zone 3, ‘sweet spot’ ride on the trainer the next day and felt totally fine,” Bernstein says. You probably don’t want to plan some epic adventure the next day or two in case you feel crappy. But unlike exercising with COVID-19, which can be unsafe, there’s no health risk to exercising after you’ve been vaccinated.

Should I Get the Vaccine If I’ve Already Had COVID?

Yes. The CDC recommends that even people who have already gotten sick with COVID-19 get vaccinated because it’s unclear how long natural immunity lasts and/or if it is based on the severity of your illness.

“The vaccine immunity appears to be stronger for many people than that following the infection, and may be longer-lasting,” Long says.

Am I Immune to COVID After I Get the Vaccine?

Not right away. “It takes a couple of weeks after the first shot to see a rise in antibodies and you don’t get full protection until a week or two after the second vaccine [which is 21 to 28 days later depending upon the type of vaccine],” Long says.

“I know people who have gotten COVID between their first and second dose,” Long says. The vaccine also prevents you from getting very ill, but not necessarily from picking up the disease and having minor symptoms or being asymptomatic.

Also, the Pfizer-BioNTech and Moderna vaccines are about 95-percent effective, which is very high, but not 100 percent. (The yet-to-be-released, single-shot Johnson & Johnson vaccine is reportedly 85-percent effective against severe disease and 66-percent effective at preventing moderate to severe infection.) So there will still be a small number of people who might still catch the virus after they are fully inoculated.

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Can I Stop Wearing a Mask After I Get the Vaccine?

Not yet. (We know. We know. We’re eager, too.) Again, the effects of the vaccines are not immediate. So you’re not protected until a couple of weeks after your booster shot. And even then, if you are inoculated, but others are not, it is possible that you could still pick up the virus and infect them, Long says.

So we will need to take the usual protections—masking, distancing, and handwashing—until the vaccine rollout allows us to reach “herd immunity,” the point at which enough of us are immunized to stop the spread. Things will hopefully continue to improve through the spring and summer into early fall if estimates remain on track, Long says.

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Selene Yeager
“The Fit Chick”
Selene Yeager is a top-selling professional health and fitness writer who lives what she writes as a NASM certified personal trainer, USA Cycling certified coach, Pn1 certified nutrition coach, pro licensed off road racer, and All-American Ironman triathlete.