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What to Know About the Coronavirus Vaccines

Questions continue as millions of Americans get immunized and boosted

Photograph of a medical vial labeled coronavirus vaccine, injection only, 5 ml
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Latest updates

  • CDC recommends updated coronavirus boosters. Just one day after the U.S. Food and Drug Administration (FDA) authorized reformulated COVID-19 boosters, the Centers for Disease Control and Prevention (CDC) officially recommended them, paving the way for the shots to be available to the public. The updated boosters, from Moderna and Pfizer-BioNTech, better target the omicron variants of the coronavirus that are currently circulating and are expected to keep causing infections this fall. “They can help restore protection that has waned since previous vaccination and were designed to provide broader protection against newer variants,” CDC Director Rochelle Walensky said about the products. CDC data shows that, on average, around 400 Americans are still losing their lives to COVID-19 every day. Adults 18 and older are eligible for the new booster from Moderna at least two months after finishing their primary series or receiving their last booster dose; people 12 and up can get the updated booster from Pfizer along the same timeline. And like the previous booster shots, which are now being phased out, the new version is free. Interested in getting the updated booster? The vaccines have started shipping, so check with your doctor or pharmacy to see if they have them in stock. 
  • FDA authorizes COVID-19 vaccine from Novavax for adolescents. The FDA has authorized Novavax’s two-shot COVID-19 vaccine series for ages 12 to 17, roughly one month after the agency OK'd its use in adults 18 and older. The company says this vaccine was shown to be 78 percent effective in trials with this age group. The two doses of this vaccine are given three weeks apart. Novavax’s product uses a different, more traditional, technology than the other COVID-19 vaccines on the market. Instead of prompting the body to make its own version of the spike protein (a key part of the virus), the protein is made in a lab and delivered directly upon injection. “If you have been waiting for a COVID-19 vaccine built on a different technology than those previously available, now is the time to join the millions of Americans who have been vaccinated,” CDC Director Rochelle Walensky said when the vaccine was first authorized for adults in July. “With COVID-19 cases on the rise again across parts of the country, vaccination is critical to help protect against the complications of severe COVID-19 disease.”
  • CDC recommends vaccinations for young children. Rochelle Walensky, M.D., director of the CDC, recommended on June 18 that parents have children ages 6 months to 5 years vaccinated, accepting the findings of the FDA and CDC’s vaccine advisory committee. “I encourage parents and caregivers with questions to talk to their doctor, nurse or local pharmacist to learn more about the benefits of vaccinations and the importance of protecting their children by getting them vaccinated,” Walensky said in a statement. The FDA on June 17 authorized the Pfizer-BioNTech and Moderna vaccines for that youngest age group and also authorized Moderna’s vaccine for ages 6 to 17. In May, health officials had recommended that kids 5 and older who have been vaccinated with Pfizer’s two-shot series get a booster.
  • ​​FDA restricts use of Johnson & Johnson COVID vaccine. Americans 18 and older who have not been vaccinated against COVID-19 should only get the Johnson & Johnson shot if the Pfizer-BioNTech and Moderna vaccines are not available or medically appropriate, or if getting the J&J product is the only way they will get vaccinated, federal regulators said on May 5 in an update to the vaccine’s emergency use authorization. The reason, the FDA noted in its announcement, is due to a rare but life-threatening complication called thrombosis with thrombocytopenia syndrome (TTS), which was first linked to the J&J vaccine in the spring of 2021. Health officials have since been monitoring and investigating all cases of TTS, which develops when blood clots form and an individual also has low levels of blood platelets. The majority of cases — there have been 60 as of March 2022 — have been in women; most have been younger than 50. TTS has not been linked to the Pfizer-BioNTech and Moderna vaccines, which use an mRNA technology different from J&J’s. The CDC in December recommended the mRNA vaccines over J&J’s product “in most situations.”
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Researchers around the world have been working at record speed to develop vaccines to combat COVID-19. Less than a year after the start of the pandemic, that goal became a reality.

Two vaccines (from Pfizer-BioNTech and Moderna) have received full approval from the U.S. Food and Drug Administration (FDA) and two others (from Johnson & Johnson and Novavax) are being administered under a limited emergency use authorization (EUA). This FDA designation allows access to treatments and other medical tools during a public health emergency when no other options exist.

What, exactly, is a vaccine?

A vaccine is something that helps a person build up immunity to an infectious disease. It works by intentionally introducing the body to an inactive form of a disease-causing germ, or something similar to it. This then stimulates the immune system’s production of antibodies, the proteins that help to protect the person from a future infection.

Think of it like a workout for your immune system: You’re “sending it to the gym and preparing it to be able to do something” in case it meets up with the germ, explains Tony Moody, associate professor of pediatrics and immunology at the Duke University School of Medicine and a principal investigator at the Duke Human Vaccine Institute. “Essentially, what a vaccine is doing is teaching the immune system how to handle something before you actually encounter the real thing — so that, hopefully, when you do encounter the real thing, you’re able to deal with it quickly and get rid of it,” he says.


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What coronavirus vaccines are available now?

The vaccines from Pfizer-BioNTech, Moderna, Johnson & Johnson (J&J) and Novavax are the only products available to Americans. The CDC recommends the Pfizer and Moderna vaccines over the J&J vaccine single-shot version because a rare but serious blood-clotting disorder has been linked to it. But J&J’s vaccine is still available for people who are “unable or unwilling to receive an mRNA vaccine,” the CDC says.

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Pfizer’s vaccine is approved for people 16 and older but is available for people ages 6 months through 15 years under emergency use authorization. Moderna’s vaccine is also authorized for kids 6 months and up and is approved for people 18 and older. Both vaccines from Novavax and J&J are authorized for people 18 and older.

The four vaccines lower your risk of getting infected with the virus and have been found to be highly effective at preventing severe illness from an infection. Hospitalizations in May 2022 were 3.8 times higher in unvaccinated individuals ages 65 and older, compared to their vaccinated and boosted peers, federal data shows.

Are the vaccines safe?

Participants in the clinical trials testing the vaccines experienced side effects, including injection-site pain, fever, chills, headaches, muscle aches and joint pain. These symptoms are usually mild to moderate in severity and are temporary. They are also in line with side effects that some people experience from other vaccines, including the flu shot and the vaccine to prevent shingles.

More serious reactions have occurred but are rare. Anaphylaxis, a severe allergic reaction, has happened in a small number of people after COVID vaccination, the CDC says. This is why you may be asked to wait about 15 minutes after your shot or booster to monitor for symptoms. Vaccines providers are equipped with medicines to quickly treat the reaction. 

Health officials are also monitoring rare reports of myocarditis and pericarditis in adolescents and younger adults who have received the Pfizer and Moderna vaccines. Most of these patients who received care responded well to medicine and felt better quickly, the CDC says.

Another uncommon event that has been linked to J&J’s vaccine is a rare but serious clotting disorder, called thrombosis with thrombocytopenia syndrome. Sixty cases of the condition were confirmed as of March; nine were fatal. Young women in their 30s and 40s are most at risk. After reviewing evidence of the adverse event, the CDC decided on Dec. 16 to recommend Pfizer’s and Moderna’s vaccines over J&J’s version; months later, the FDA limited its use. J&J’s vaccine, however, is still available to those who are “unable or unwilling” to get the Pfizer or Moderna vaccine.

What's more, booster shots are recommended for people who have been fully vaccinated. People 12 and older are eligible for an omicron-specific booster from Pfizer at least two months after their last shot (including a booster shot); people 18 and older can opt for a similar one from Moderna along the same timeline. Experts expect these updated boosters will provide better protection against the coronavirus variants that are currently circulating and are expected to keep spreading this fall and winter.


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How much does the vaccine cost?

The federal government purchased hundreds of millions of vaccine doses with taxpayer money, so Americans do not have to pay to receive them, including the booster shots, though this could change in the future.

Can I still get COVID-19 after getting the vaccine?

Because no vaccine is 100 percent effective, breakthrough infections can occur, and more are being reported as omicron and its subvariants rip through the country. But experts stress that the vaccines and boosters remain highly protective against hospitalization and death.

Breakthrough infections, however, can contribute to the spread of COVID-19, which is why health officials recommend that vaccinated individuals in areas of high community transmission wear a face mask in indoor public settings.

Do I need the vaccine if I have already had COVID-19?

Even if you had COVID-19, the CDC recommends getting vaccinated and boosted, since research has not yet shown how long protection from a previous coronavirus infection lasts. Plus, the vaccine may afford better protection against COVID-19 than a previous infection. Unvaccinated people who already had COVID-19 had greater odds of getting COVID-19 again, compared to fully vaccinated people, CDC study found

Have questions? Talk to your doctor.

Is it good to have more than one vaccine available?

Absolutely. “In fact, it’s highly desirable,” says William Schaffner, an infectious disease expert and professor at Vanderbilt University School of Medicine, because that would mean “there would be more vaccine manufacturers working to actually produce the vaccine, and so we could more expeditiously try to vaccinate the population in the United States and beyond.”

Kathleen Neuzil, professor in vaccinology and director of the Center for Vaccine Development and Global Health at the University of Maryland School of Medicine, echoes Schaffner’s sentiment and points to the flu vaccine for comparison: There are multiple formulations on the market, including the injectable high-dose vaccine and the nasal spray vaccine, for example, which are recommended for different populations.​“We really need every person on Earth, theoretically, to be able to receive this vaccine. So, to me, [having more than one option] is a positive, because we need so much,” she adds.​

Editor’s note: This article, originally published May 1, 2020, has been updated to reflect new information.


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