This article was last updated October 1, 2021.
We rounded up the most common questions about the COVID-19 vaccines—like how many vaccines are available, common side effects, safety and effectiveness, and what to expect after you get vaccinated—and asked medical experts for the answers.
Though new information comes out almost daily, what is certain is that getting the vaccine will keep you safe and the benefits of getting it far outweigh any risks you may have heard about.
When can I get the vaccine?
The vaccine has been rolled out in phases, with the most at risk being vaccinated first. As of May 2021, children 12 years and older and all adults are eligible for a vaccine in every state.
To find out how to register for the vaccine, check with your county or state health department, or call your doctor. There are also apps to help you find available vaccine slots and you can search on pharmacy websites.
How much will I pay for the vaccine?
You should not pay anything—the vaccines are free to Americans. You should not be asked to pay a copay either. Still, you may be asked for your health insurance information when registering for the vaccine. Doctors and medical systems can get paid by your insurance company to administer the vaccination.
What are the side effects of the vaccine?
After you are vaccinated, you may experience soreness, redness, or swelling in your arm. Within the next day or two, you may feel like you’ve been hit with the flu. You might have fatigue, headache, muscle aches, nausea, chills, and fever. Some people have no side effects while others have intense chills. You may have to call in sick from work for a day.
Side effects of all three vaccines are similar. For the vaccines that require two doses, side effects are more common after the second dose. Although those who have had COVID are more likely to report side effects with the first dose.
Keep in mind that these effects are a healthy sign that your immune system is responding to the vaccine.
Experts don't recommend taking over-the-counter pain medication, such as ibuprofen or acetaminophen, to prevent side effects before you get the shot in case it interferes with your immune response. But they agree that it’s safe to take over-the-counter pain medication, such as acetaminophen if you have symptoms from the shot. (Be sure to read the label of any over-the-counter medication to make sure it’s safe for you.)
What’s the difference between the vaccines?
There are three available vaccines. Two vaccines—Pfizer and Moderna—require two shots, separated by about 3 to 4 weeks.
The third vaccine is from Johnson & Johnson, and it only requires one shot.
The Moderna and Pfizer vaccines are for ages 12 and older, while those 18 and older can get the Johnson & Johnson vaccine.
If you get a two-dose version, you should sign up to get the same vaccine as your first shot, if possible.
Why do I need two shots?
The Pfizer and Moderna vaccines require two doses, similar to other vaccines like HPV, shingles, and hepatitis B. The first vaccination helps to spark the immune response but is only about half as effective as having both doses. The second dose boosts the response to its full potential and gives long-term protection.
What about a third shot?
A booster shot is now available to help protect you against the delta variant of COVID and make sure your immune system continues to protect you from getting seriously ill from COVID.
The CDC currently recommends a booster shot for certain groups of people. Visit the CDC’s website for the latest booster vaccine recommendations.
How long does it take for it to work?
It takes time for your immune system to start producing antibodies that protect you against COVID.
It takes about 2 weeks after the Johnson & Johnson vaccine for it to provide protection. With the two-dose vaccines, you are partially protected after the first shot. It takes 2 weeks after your second vaccine to provide protection. While the vaccines are very good at preventing you from getting COVID, it is possible to get infected (called a breakthrough infection). If you do, the vaccines will help prevent you from getting very sick, needing to be hospitalized, or dying.
How can I be sure it’s safe?
Before the FDA approves a vaccine, medical researchers conduct large clinical studies to show that the vaccine is safe and effective. The trials of tens of thousands of people showed that the COVID vaccines are very safe.
In rare instances, people who got the vaccines have had an extreme allergic reaction known as anaphylaxis. If you have had an allergic reaction to a vaccine in the past, even if it was not severe, the CDC recommends that you talk to your doctor, who can help you decide if it is safe for you to get vaccinated.
For adult women younger than 50 years old who receive the Johnson & Johnson vaccine, there is an extremely rare risk of blood clots. To learn more, visit the CDC website.
Can I return to normal activities after getting the vaccine?
It takes 2 weeks after your second dose of the Pfizer or Moderna vaccines and 2 weeks after your only dose of the Johnson & Johnson vaccine before you are well protected.
But it's still possible (though a lot less likely) to catch COVID. With the Delta variant on the rise, the CDC recommends wearing masks indoors in public, if you are in an area of substantial or high transmission.
If you are vaccinated, you generally do not need to wear a mask outdoors, unless you are in a crowded area with high transmission and in close contact with people who are not fully vaccinated. People with a weakened immune system may not be fully protected even if they are fully vaccinated and should continue to take precautions such as masking and social distancing.
Is it safe to get the vaccine if I already had COVID?
While it’s safe to get the vaccine if you had COVID, it’s recommended that you wait until you have recovered and no longer need to isolate. If you were treated with monoclonal antibodies or convalescent plasma, wait 90 days before getting vaccinated. Check with your doctor about when to get the vaccine.
And you still need to get the vaccine. Experts don’t know how long immunity from COVID lasts after being sick. It is possible to get COVID again even if you already had it.
What can I expect when I get the vaccine?
It takes just a few seconds for a nurse or other healthcare provider to give you the vaccine. The injection is in your arm. You should be told to wait 15 minutes before leaving in case of an allergic reaction—30 minutes if you have a history of allergies to medications. (If you have an EpiPen—epinephrine—bring it with you, though all vaccination sites should be equipped with EpiPens.)
You will be given a card with the date you were vaccinated and the name of the vaccine you received. Put it in a safe place (take a photo of it in case you lose it). If you get the Pfizer or Moderna vaccine, bring the card to your second appointment. You should make an appointment for your second shot before you leave, if possible.
Is it a problem that they were developed so quickly?
A number of factors helped speed up the process without sacrificing safety.
The technology behind the Pfizer and Moderna vaccines has been studied for more than a decade. And researchers were able to switch gears very quickly to focus on the coronavirus. Called mRNA, this technology makes it possible to produce vaccines much more rapidly than traditional vaccines. The Johnson & Johnson vaccine uses more conventional technology.
Can children get the vaccine?
Currently, people ages 12 and up are eligible for the Pfizer vaccine. People ages 18 and up are eligible for the Moderna and Johnson & Johnson vaccines. A vaccine for children between the ages of 2 and 11 is expected to be available by the fall or winter of 2021.
Can I get the vaccine if I’m pregnant or breastfeeding?
The CDC recommends that women who are pregnant, recently pregnant (within 6 weeks of delivery), or breastfeeding get a COVID vaccine. Discuss any questions you have with your doctor.
Pregnant and recently pregnant women have a greater risk of serious illness and poor pregnancy outcomes from COVID. While pregnant and breastfeeding women weren’t included in the first vaccine studies, both Pfizer and Moderna are monitoring people who became pregnant during the clinical trials.
Keep in mind that the vaccines don’t contain the live virus and can’t give you or your baby COVID, either from the vaccine or through breast milk.
Are companies or businesses allowed to require vaccination?
Possibly. According to legal experts, employers may be able to require employee vaccinations if not vaccinating them could directly threaten other employees in the workplace. Employers would have to make exceptions for workers who can’t get vaccinated because of disabilities or due to religious beliefs.
The Equal Employment Opportunity Commission (EEOC) has found that COVID is a direct threat to other employees. But the commission hasn’t said how it will treat mandatory vaccine policies yet.
The scientific understanding of COVID-19 as well as guidelines for its prevention and treatment are constantly changing. There may be new information since this article was published. It’s important to check with sources like the CDC for the most up-to-date information.
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