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What to Know About the Coronavirus Vaccines

Optimism surges and questions arise with immunization efforts underway

image of a vial labeled coronavirus vaccine

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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 is now a reality. The U.S. is among the countries that have begun vaccinating people against a virus that has so far infected more than 25 million people in the United States; it’s killed more than 421,000 Americans and more than 2.1 million people globally. As noted above, two vaccines, one from Moderna and another from Pfizer-BioNTech, are now being distributed in the U.S., first to health care workers and staff and residents of long-term care facilities, next to people 65 and older and frontline essential workers.

Both vaccines received an emergency use authorization (EUA) from the FDA. An EUA is a green light, of sorts. It is not the same as official approval.

During a public health emergency, such as the coronavirus pandemic, the FDA can authorize in a timely manner previously unapproved medical products to diagnose, treat or prevent the illness of concern when there are no other approved or available alternatives. The EUA process is faster than standard FDA approval, which can take six to 10 months. However, data proving safety and effectiveness are still required for authorization, and the FDA and an advisory committee of experts use this data to weigh the risks and benefits of the product in question.

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 if he ever comes across the real germ.

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 when it encounters the real thing in the future,” says Tony Moody, associate professor of pediatrics and immunology at 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.”

In the case of the new coronavirus, a vaccine makes a person resistant to an infection from the virus and the illness it causes — COVID-19 — or, at least, enables a person who becomes infected to have “a shorter course [of disease] or not as many complications,” Moody adds.

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What coronavirus vaccines are available now?

The three vaccines that have received EUAs - Pfizer-BioNTech, Moderna and Johnson & Johnson - are so far the only products available to Americans.

Pfizer’s vaccine was given emergency authorization by the FDA for use in people 16-years-old and older, making it the first coronavirus vaccine available to the American public.

Moderna and J&J's vaccines have now been authorized for people 18 and older.

The three vaccines have been found to be highly effective at preventing COVID-19 in clinical trial participants. Pfizer-BioNTech's two-dose vaccine is about 95 percent effective against COVID-19, regardless of age, race or other risks for severe illness from an infection, an FDA analysis shows. And Moderna’s proved to be about 94.5 percent effective against COVID-19 in people of all ages, genders and ethnicities. J&J’s product has been found to be 66 percent effective overall and 72 percent effective in the United States.

Are the vaccines safe?

Safety is a key concern among health officials and experts. Participants in the Pfizer-BioNTech, Moderna and Johnson & Johnson trials experienced side effects after vaccination, including injection-site pain, fever, chills, headaches, muscle aches and joint pain. These symptoms are temporary and are in line with side effects some people experience from other vaccines, including the flu shot and the vaccine to prevent shingles.

The CDC has documented several cases of anaphylaxis in U.S. vaccine recipients. Though an anaphylactic reaction is potentially life-threatening, it can be quickly halted as it was in these six cases, with medicines such as epinephrine. Because of this, the CDC is recommending that anyone who has ever had a severe allergic reaction to any ingredient in a COVID-19 vaccine abstain from receiving it. If you have a history of severe allergic reactions to other vaccines, ask your doctor if you should get a COVID-19 vaccine, the agency advises.

After a vaccine is authorized, many vaccine safety monitoring systems watch for adverse events, according to the CDC. If one is discovered, “experts quickly study it further to assess whether it is a true safety concern” and then adjust vaccine recommendations as needed, the agency explains.  

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How are the vaccines being distributed?

The federal government is overseeing the distribution and tracking of coronavirus vaccines in the U.S., but state and local officials are prioritizing who gets the vaccine in their jurisdictions. The government is also partnering with private companies to ensure high-risk individuals can easily access a vaccine. Health care workers and residents and staff of long-term care facilities were in the first group targeted for vaccination; the CDC recommends that the next group of Americans to receive a COVID vaccine should be adults age 75 and older. However, many states prioritized all adults age 65 and older after the federal government directed states to expand distribution in order to get the vaccine out faster. The next group for vaccination under CDC guidelines would be frontline workers, including first responders, postal workers, teachers, public transit workers and people who work in grocery stores.

Officials predict it will take several more months to vaccinate everyone who wants a vaccine, even as production ramps up and more vaccine candidates clear authorization.

There are logistical considerations, including the need to ensure proper transportation and storage for the vaccines. Both the Pfizer and the Moderna vaccines require cold storage at specific temperatures but the J&J vaccine is able to be shipped and stored at conventional refrigeration temperatures.

How much does the vaccine cost?

The federal government pre-purchased hundreds of millions of vaccine doses with taxpayer money, and Americans will not have to pay to receive them.

Vaccine providers are able to charge an administration fee for giving the shot, but this fee should be covered by public or private insurance, or by a government relief fund for the uninsured.

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

It’s unclear whether someone who’s been vaccinated can still become sick with COVID-19 and how long immunity will last, although more details on the vaccine’s effectiveness should emerge in post-trial surveillance.

“That’s something that the recipients will have to understand when they get the vaccine,” says William Schaffner, an infectious disease specialist and professor of preventive medicine at the Vanderbilt University School of Medicine. “The vaccine provides protection, but it won’t be like a suit of armor.”

Schaffner’s main message: Just because you roll up your sleeve and get the shot doesn’t mean you can throw away your mask and disregard other prevention efforts such as social distancing and handwashing. Those will be crucial “for quite some time” in order to get control over the virus, Schaffner says.

Are both doses really necessary?

Both the Pfizer-BioNTech and Moderna vaccines require two doses and following through with both doses is necessary to ensure effectiveness. The J&J vaccine only requires one dose.

According to the CDC, the first shot starts building protection, while the second shot “is needed to get the most protection the vaccine has to offer.”

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

The verdict is still out when it comes to how long you are protected from COVID-19 after a previous infection — what's referred to as natural immunity. In fact, “early evidence suggests natural immunity from COVID-19 may not last very long,” the CDC explains. Because of this, “people may be advised to get a COVID-19 vaccine even if they have been sick with COVID-19 before,” the agency states.

Health officials will keep the public informed of any developments and recommendations as more is learned about the duration of natural immunity.

“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.”


Tony Moody, M.D., associate professor of pediatrics and immunology at Duke University School of Medicine and a principal investigator at the Duke Human Vaccine Institute

Is it good to have more than one vaccine?

Absolutely. “In fact, it’s highly desirable,” Schaffner says, 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, M.D., 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, has been updated to reflect new information.

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