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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
Manjurul/Getty Images

Latest updates

New boosters provide “significant additional protection” against COVID-19. A new study from the Centers for Disease Control and Prevention (CDC) finds the updated bivalent boosters — which target omicron subvariants BA.4 and BA.5, along with the original strain of the coronavirus — provide additional protection against symptomatic COVID-19 in people already vaccinated with the original (monovalent) vaccine formula. The study is the first to look at the effectiveness of the new booster in a real-world setting at a time when descendants of the omicron variant are dominating in the U.S. On the heels of the report’s release, White House officials announced a six-week campaign to get more Americans vaccinated and boosted ahead of the holidays and cold-weather months, when respiratory illnesses abound. The government is expanding the number of sites administering vaccines, including mobile sites and pop-up sites, and is working to make sure vaccine education is available in nursing homes throughout the U.S. “We’re doing everything we can in the next six weeks to help families get the updated COVID shots by the end of the year, because it’s the best protection for this winter,” White House COVID-19 Response Coordinator Ashish Jha said. The boosters are authorized for Americans age 5 and up. Visit to find a vaccine site nearest you. 

CDC authorizes Novavax booster for adults. Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky has approved the Novavax COVID-19 booster for adults age 18 and older. In her decision memo, Walensky gives these adults the option “to receive a Novavax monovalent booster instead of an updated (bivalent) Pfizer-DBioNTech or Moderna booster if they have completed primary series vaccination but have not previously received a COVID-19 booster — and if they cannot or will not receive mRNA vaccines.” This authorization comes on the heels of Novavax’s two-shot COVID-19 vaccine series being approved for ages 12 to 17 as well as for adults 18 and older. The two doses of the Novavax 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,” 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.”

New COVID boosters could prevent up to 90,000 deaths this fall and winter. If 80 percent of Americans who are eligible for the new COVID-19 omicron boosters get the vaccine by Dec. 31, nearly 90,000 deaths and more than 936,700 hospitalizations due to COVID-19 could be prevented, a new report from the Commonwealth Fund shows. If COVID booster uptake is even equivalent to last year’s flu vaccine uptake, more than 75,000 deaths and 745,409 hospitalizations due to COVID-19 could be prevented. The boosters could also save the U.S. billions in medical costs, the report finds. As of Nov. 21, about 11 percent of eligible Americans have received the new booster, CDC data shows. ​​​​​​​​

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.

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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.

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.

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. The vaccine from Novavax is authorized for people 12 and up, and J&J’s shot is authorized for adults 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 age 65 and older, compared to their vaccinated and boosted peers, federal data shows. Updated booster shots from Pfizer and Moderna are also available and recommended for people age 5 and older. These new vaccines (known as bivalent boosters) target the original strain of the coronavirus and also the omicron subvariants that are currently driving the majority of infections in the U.S. to provide a broader swath of protection.

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.

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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. Vaccine 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,Moderna and Novavax 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.

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.



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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, a 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.