Your questions about a coronavirus vaccine, answered

In the battle against COVID-19, millions of doses of the two authorized vaccines have already been distributed

FILE - This May 4, 2020, file photo provided by the University of Maryland School of Medicine, shows the first patient enrolled in Pfizer's COVID-19 coronavirus vaccine clinical trial at the University of Maryland School of Medicine in Baltimore. The German pharmaceutical company BioNTech and its U.S. partner Pfizer say they have submitted an application for conditional approval of their coronavirus vaccine with the European Medicines Agency. (Courtesy of University of Maryland School of Medicine via AP, File)
FILE - This May 4, 2020, file photo provided by the University of Maryland School of Medicine, shows the first patient enrolled in Pfizer's COVID-19 coronavirus vaccine clinical trial at the University of Maryland School of Medicine in Baltimore. The German pharmaceutical company BioNTech and its U.S. partner Pfizer say they have submitted an application for conditional approval of their coronavirus vaccine with the European Medicines Agency. (Courtesy of University of Maryland School of Medicine via AP, File) (University of Maryland School of Medicine)

In a remarkably short period of time—less than one year—scientists have managed to design, create, and test several potential vaccines for SARS-CoV-2, the virus that causes COVID-19. On Dec. 11, the Food and Drug Administration issued the first emergency use authorization for a coronavirus vaccine, the one developed by Pfizer and BioNTech. On Dec. 18, the FDA issued a second emergency authorization, for a vaccine developed by Moderna, which is based on similar technology.

Healthcare workers in the U.S. started getting the Pfizer vaccine Dec. 14 and the Moderna vaccine the following week. The Centers for Disease Control and Prevention report that as of Jan. 4, at least 15 million vaccine doses have been distributed in the U.S., and at least 4.5 million people have received their first of two doses.

In a Consumer Reports nationally representative survey of 2,851 U.S. adults, 63 percent said they are very or somewhat likely to get a vaccine when one becomes available. (The survey was fielded in early to mid-November; that number may well rise as more vaccine doses are administered across the country.)

For those trying to understand all the vaccine news and how it will affect their lives, a number of questions remain. Consumer Reports has reviewed government guidance and consulted with experts to answer some of the most common questions. (Don’t see your question here? Send it to CR at covidquestions@cr.consumer.org, and we may answer in an update to this article.)

When Will I Get Access to a Vaccine?

The Advisory Committee on Immunization Practices, an expert group that makes official vaccine recommendations to the federal government, has worked with the CDC to determine who should get priority access to a vaccine. That will be especially important initially, when supply is limited.

The ACIP has recommended that healthcare personnel and residents of long-term-care facilities, including skilled nursing facilities, nursing homes, and assisted living facilities, be offered access first to a coronavirus vaccine.

After that, recommendations are to roll out the vaccine to people in essential roles or who are particularly vulnerable to infection. Though specifics are still under discussion, the next groups likely to receive vaccines include essential workers, such as teachers, food service workers, manufacturing personnel, and police officers and firefighters. People with medical conditions that put them at high risk for severe COVID-19 and adults 65 and older are also high priority. Nonessential workers and people at lower risk of severe illness would be lower on the priority list.

Moncef Slaoui, PhD, the chief scientific adviser at Operation Warp Speed, the federal government’s initiative to accelerate vaccine development, told CNN on Dec. 6 that healthcare workers and people in long-term-care facilities could be vaccinated by mid-January. He said that by March, 100 million high-risk people could be vaccinated. People at the lowest risk could have access to the vaccine by June, he told the Washington Post. He emphasized, however, that things might not go exactly according to plan, because the manufacture and distribution of biologic products like vaccines is complicated.

So far, rollout has been slower than hoped. On Dec. 17, Pfizer released a statement saying that the company had millions of doses sitting in a warehouse but had not received shipment instructions for where to distribute them. There have been reports from The New York Times and other outlets that millions of doses could expire before they are given. There are approximately 21 million healthcare workers and 3 million residents of long-term-care facilities; giving all of them a first dose by mid-January would require speeding up the rate of vaccination significantly.

What Does It Mean for the FDA to Provide Emergency Use Authorization?

Because of the public health crisis caused by the ongoing pandemic, the FDA is empowered to provide expedited permission to distribute a vaccine to certain populations (such as healthcare workers) before fully approving a vaccine, provided the vaccine meets certain standards for safety and efficacy. This would be an emergency use authorization, designed to more quickly and easily enable use of a vaccine, according to the agency.

After a full evaluation of all safety and efficacy data, which takes more time, the FDA may fully approve the vaccine for use among a wider population.

How Will a Vaccine Rollout Work?

The federal government will have a centralized system to order, distribute, and track vaccines, according to the CDC. Vaccines will be ordered through the CDC.

States, however, will have flexibility in how they distribute vaccines, according to Kathleen Neuzil, MD, a professor of vaccinology and director of the Center for Vaccine Development and Global Health at the University of Maryland in Baltimore. Because of that, there may be some variation in the ways states distribute vaccines to priority populations, she says.

Where Will I Be Able to Get a Vaccine?

Vaccines will be distributed at a wide variety of locations, including hospitals, long-term-care facilities, mobile and temporary clinics, doctors’ offices, and pharmacies, according to the CDC.

Cold storage requirements may limit where certain vaccines can be distributed, at least initially, according to Neuzil. The Pfizer vaccine, for example, currently needs to be stored in extremely cold conditions, which may make it a better candidate for distribution at a hospital with adequate storage facilities.

Will Coronavirus Vaccines Be Free?

Yes. The U.S. government will pay for vaccines given to Americans, according to the CDC.

Providers may charge a fee for administering the vaccine, but the government has mandated that insurers (or the government, in the case of uninsured individuals) cover this fee, so people should not have any out-of-pocket expenses associated with vaccination.

How Long Does Protection Take to Kick In?

The Moderna and Pfizer vaccines, like most of the other vaccines that are in or have completed the last stage of trials before being submitted to the FDA for approval, require two doses—an initial shot and a booster, usually several weeks later. Generally with a two-dose vaccine, it takes about two weeks from the second dose for a vaccine’s protection to fully kick in, according to Natalie Dean, PhD, an assistant professor of biostatistics specializing in infectious disease and vaccine development at the University of Florida in Gainesville.

But though both doses are necessary, the FDA’s analysis of the Pfizer vaccine indicates that people appear to be somewhat less likely to get COVID-19 within two weeks of receiving the first dose. It’s unclear how long protection from that first dose may last. And the second dose is still required for full protection, to ensure a more durable immune response.

How Long Will Protection Last?

It will take time and more research before we know how long vaccine-provided immunity lasts, according to the CDC.

The early evidence scientists have on how long natural immunity lasts after an infection with SARS-CoV-2 has been mixed. But scientists hope immunity from a vaccine is more durable. If it turns out that vaccine-induced immunity wanes after time, occasional booster shots may be needed, experts say.

If I Had COVID-19, or Think I Did, Should I Still Get Vaccinated?

According to the CDC, researchers don’t yet know how long people are protected from reinfection after recovering from COVID-19, and there aren’t recommendations for whether people who have recovered from the virus should get a vaccine. However, at least some of the vaccine trials have included people who had recovered from COVID-19, according to Neuzil, the vaccinology professor at the University of Maryland, and it appeared to be safe for these people to get the vaccine.

Even if recovered patients have some natural immunity, the vaccine could provide some longer-term benefit, she says. The immune system’s natural response to a SARS-CoV-2 infection is varied, and in some cases, protection may not last very long. Though we still don’t know how long protection from vaccination will last, initial data indicates that vaccines can create a strong immune system response.

Can We Really Know Yet If a Vaccine Is Safe?

Before granting even emergency use authorization, the FDA said manufacturers must provide at least two months of safety data on people who received the vaccine. Already, in the trials for the two leading vaccine candidates, the agency has two months of safety data on at least 35,000 participants who received real vaccines, not placebo shots.

So far, side effects from the leading candidates have been similar to effects from other vaccines, including fever, headaches, feeling run-down, and soreness in the arm, C. Buddy Creech, MD, MPH, director of the Vanderbilt Vaccine Research Program and a principal investigator on coronavirus vaccine efforts by Moderna and Johnson & Johnson, said on a call organized by the Infectious Diseases Society of America.

Typically, any vaccine side effects would emerge during these first two months after immunization, he says, and it’s difficult to clearly link any adverse health events that occur after two months with a vaccination. However, regulators will continue to monitor vaccine trial participants for two years to see how long immunity lasts and to monitor for any adverse events. Regulators will also track people who receive the vaccine in the real world because it’s possible that an extremely rare side effect could emerge once millions of people receive the vaccine. (For more on reports of allergic reactions that several vaccine recipients have experienced, see the question below.)

“Even though the process has been expedited in association with the review of this EUA, the FDA’s expert review staff has reviewed thousands of pages of technical information,” FDA Commissioner Stephen Hahn said in a statement. The recommendation for an emergency use authorization is made by an independent panel of experts, he explained.

For more on this question, see our earlier article.

What Should I Know About Reports of Allergic Reactions to the Vaccine?

In the U.K., where authorities started distributing the Pfizer vaccine to healthcare workers and high-risk patients starting on Dec. 8, regulators have advised that anyone with a history of a severe, potentially life-threatening allergic reaction called anaphylaxis to a vaccine, medicine, or food should not receive the vaccine while researchers review two reports of healthcare workers who had severe allergic reactions after receiving the vaccine.

This announcement raised concerns during the FDA advisory panel’s review, which comes before the agency’s authorization, with some experts worried that it could frighten people with allergies and make them think they could not get the vaccine.

At least two healthcare workers in Alaska also experienced allergic reactions after receiving the Pfizer vaccine. One was hospitalized. The FDA is working with the CDC and with U.K. public health agencies as they continue their investigations, said Doran Fink, deputy director of FDA’s Division of Vaccines and Related Products Applications, during the advisory panel’s discussion of the Moderna vaccine.

Fink emphasized that the FDA learned about the U.S. cases because the systems set up to flag issues with the vaccine are working as designed.

As of Dec. 28, there were at least 10 reports of people developing allergic reactions after receiving the Pfizer-BioNTech vaccine, and at least two reports of allergic reactions among people who received the Moderna vaccine, according to a review of research published in The Journal of Allergy and Clinical Immunology: In Practice.

Guidelines for administration of both vaccines specify that facilities providing vaccines should be prepared to manage severe allergic reactions.

There were no severe allergic reactions in the Pfizer trial, which excluded people who had previously had severe allergic reactions to vaccines, a Pfizer scientist said during the advisory panel’s discussion. The FDA’s earlier review of Pfizer’s trial data found slightly more potential minor allergic reactions in the group that received the vaccine than in the placebo group, but none of these were severe, and none occurred immediately after people received their doses of vaccine.

The Moderna trial, which did not exclude participants who had severe allergic reactions in the past, had no severe anaphylactic allergic reactions occur at any time close to vaccine administration.

For now, the FDA says data continues to support the use of Pfizer’s vaccine without any new restrictions. The only people being told to avoid the vaccine are those allergic to vaccine ingredients.

The authors of the research review concur with FDA and CDC guidance on vaccine administration. To minimize risk while maximizing the number of people vaccinated, they suggest vaccine administrators ask patients about allergy history. People who report being allergic to a vaccine component should be given a skin test and should not receive the vaccine if that test is positive.

If patients report a history of severe allergies to food, medication, or other vaccines or injectable medications, the authors write that the vaccine can still be given, and that those vaccine recipients should be observed for 30 minutes after getting their vaccine dose.

How Many People Need to Be Vaccinated for Normal Life to Resume?

Scientists don’t yet know, according to the CDC. Once enough people have some immunity, either because of previous infection or because of vaccination, the virus will have a hard time spreading through the community. Once that community protection exists, it may be possible to resume what we thought of as “normal” prepandemic life.

More research needs to be done before scientists can say exactly how many people need to be vaccinated. It’s possible that with extremely effective vaccines, we might hit the point where communities are protected by the time somewhere between 60 and 70 percent of people have been vaccinated, according to Neuzil at the University of Maryland.

How Many Vaccine Doses Will the U.S. Need?

All but one of the COVID-19 vaccines that are currently in or have completed Phase 3 clinical trials in the U.S. (for more on the stages of vaccine trials, see our article on vaccine development) need two shots to be effective, according to the CDC. In most cases, that means that 100 million doses of a vaccine will be enough for 50 million people. There are about 250 million adults in the U.S., so we are likely to need 500 million doses to vaccinate everyone 18 and up. (The vaccine is still being tested in children.)

Pfizer is expected to be able to provide 100 million doses to the U.S. by March, according to the New York Times. The company expects to have 50 million doses available globally by the end of 2020, but those will be distributed among all the countries with purchase agreements that have approved the vaccine. Moderna expects to have 20 million doses of vaccine available in the U.S. by the end of 2020, and between 85 and 100 million doses available in the U.S. in the first quarter of 2021.

Because vaccine doses are limited, there have been discussions about whether to try to stretch available vaccine further. Ideas to do so include giving people one dose instead of two, having people wait longer between doses to help more people quickly get a first dose, giving a half-dose of a vaccine, or mixing and matching vaccines, depending on what’s available, according to the FDA.

The U.K.’s vaccine advisory panel, for example, has recommended that first doses be administered to as many people as possible, even if it means many could wait up to three months for their second dose.

It’s reasonable to conduct clinical trials to see whether any of these are viable strategies, says Gregory Poland, MD, a professor of medicine who studies vaccine response in adults and children, and director of the Vaccine Research Group at the Mayo Clinic. But right now there’s limited to no data to support these ideas, he says, so they should be studied further before being implemented.

“In the history of medicine, the pages are littered with things everybody agreed made sense but when you tested offered no benefit, or harm,” he says. However, he says research should continue, in case the situation becomes more desperate in coming weeks.

On Monday, the FDA released a statement saying it’s reasonable to consider and evaluate alternate dosing regimens in clinical trials, but that because there was no data supporting any changes in vaccine procedures for now, no changes to vaccine schedules should be made.

What Do the Efficacy Numbers Really Mean?

Pfizer and Moderna, manufacturers of two of the first vaccines that are likely to be authorized or approved by the FDA, reported that their vaccines appeared to be at least 90 percent effective at preventing people from developing symptoms of COVID-19 in clinical trials.

In vaccine trials, roughly an equal number of participants receive the real vaccine or a placebo. Pfizer calculated that its vaccine was approximately 95 percent effective, for example, after observing that 172 out of the 181 COVID-19 cases that occurred in trial participants were in the placebo group—demonstrating that people who received the vaccine appear to be generally well-protected.

Though these trials are able to show that a vaccine is effective, it’s possible that the degree of effectiveness in a real-world setting could vary, according to the CDC. Real-world situations, including the ways vaccines need to be stored or transported, and the health of people receiving the vaccine, could result in a different degree of efficacy.

Plus, while manufacturers have done their best to test vaccines in a variety of populations, including people of different ages and races, and with different medical conditions, it’s possible that vaccines will turn out to be more or less effective in certain populations, according to Paul Offit, MD, an attending physician in the division of infectious diseases at Children’s Hospital of Philadelphia and director of the hospital’s Vaccine Education Center. Offit also was a member of the FDA advisory panel.

Is It Unexpected That Some Vaccines Report 95 Percent Efficacy?

Before data from trials of these vaccines started to come in, researchers were hoping to see that the vaccines were 70 or 75 percent effective, according to Offit. FDA guidelines required the vaccines to be at least 50 percent effective to be considered for authorization.

Seeing that the Pfizer and Moderna vaccines were significantly more effective than that was “extraordinary,” Neuzil says. That indicates that it will be possible to have a significant impact on this pandemic and that some of the new vaccine technologies that were used during the development of these vaccines may come in handy for other viral outbreaks in the future.

It’s possible that “we enter into a golden age of vaccinology by having these types of new technologies,” says Creech at the Vanderbilt Vaccine Research Program.

Why Are There So Many Different Kinds of Vaccines?

There are so many different types of vaccines because many scientists and pharmaceutical companies started working on this problem at the same time, using as many different approaches as they could think of.

Some of the coronavirus vaccines that are furthest along in development, including the ones made by Moderna and Pfizer, rely on new technologies that have never been used in an approved vaccine before, according to Dean at the University of Florida. Normally, the barrier for trying to develop a new vaccine is cost, says Paul Duprex, PhD, a professor of microbiology and molecular genetics and director of the Center for Vaccine Research at the University of Pittsburgh. But in this case, the federal government decided to step in to cover the financial risk.

Many of the new technologies being used in this first batch of vaccines were designed for emergencies, says Dean, leading to fast development. It was important to try a variety of approaches, according to Neuzil, because there was no certainty that any one approach would work out. But the vaccines that are furthest along all have at least one thing in common—they target the specific protein (known as the spike protein) that SARS-CoV-2 uses to infect cells.

The Moderna and Pfizer vaccines that are furthest along also use the same technology, called mRNA (more on that below). Given all these similarities, it’s reassuring to see that both have similar efficacy, Neuzil says.

How Are These Vaccines Made, and What Technology Do They Use?

The Pfizer and Moderna vaccines rely on a technology known as messenger RNA, or mRNA.

To make an mRNA vaccine, researchers insert a bit of the genetic code from the virus into a lipid coating that can be injected into the body. Our cells use that code to create a harmless piece of the protein that SARS-CoV-2 uses to infect cells—without the dangerous parts of the virus. This teaches our immune system to recognize and respond to that protein, so the immune system is then able to fight off an infection from the real virus.

The advantage of this technology, according to Neuzil, is that it was very fast to create a vaccine once scientists had identified the genetic sequence for the SARS-CoV-2 virus. Because this approach hadn’t been used for a vaccine before, scientists didn’t know how well it would work.

How Might Mutations Affect the Vaccine?

Headlines about coronavirus mutations and new, seemingly more contagious variants of the virus, have some wondering whether vaccines will still be effective. In particular, one virus variant first detected in the U.K. and since found in the U.S. and around the world, is a source of concern.

Vaccines teach our immune system to respond to a virus by recognizing some key sign of it. Mutations that affect the parts of the virus the immune system recognizes can help a virus thwart a vaccine’s effectiveness.

The Pfizer and Moderna vaccines, like many of the vaccines currently furthest along in development, target a particular protein—the spike protein—that the coronavirus uses to infect people. So mutations of that protein could potentially make a vaccine less effective, says Poland, of the Vaccine Research Group at the Mayo Clinic.

But even if the mutations in current variants of the virus have some impact on the vaccines’ efficacy, it’s likely that the vaccines could still be highly effective, he says.

Still, we may eventually need new vaccines that target other parts of the SARS-CoV-2 virus, Poland wrote in a commentary for the journal Vaccine, where he’s the editor-in-chief.

Will I Be Able to Choose Which Vaccine I Want?

Initially, it’s likely that demand for vaccines will be higher than supply, Neuzil says, meaning people aren’t likely to be able to choose one vaccine over another.

As more vaccines become available, and if we learn that certain vaccines work better or come with fewer side effects for certain population groups, one vaccine might be recommended over another for specific groups of people, as is the case now with flu vaccines.

When Will Testing Happen in Children and Pregnant People?

Pfizer’s vaccine was tested in and authorized for individuals ages 16 and older. Moderna’s has been authorized for individuals 18 and older. Younger children and pregnant people were excluded from the initial vaccine trials. Companies including Pfizer and Moderna are now conducting trials in children as young as age 12.

Before testing the vaccine in pregnant people, manufacturers have been completing what are known as developmental and reproductive toxicity studies in animals, Neuzil says. These trials are now being finished, she says, which could mean that testing in pregnant people could begin in the coming months. In the meantime, guidance from the Advisory Committee on Immunization Practices permits individual pregnant people to choose to get the vaccine if they are part of a group that’s currently eligible to be vaccinated, like hospital workers.

Can Vaccinated People Still Spread the Virus?

We don’t yet know. The primary goal of vaccine trials has been to see whether trial participants become sick with COVID-19, not to test everyone in the trials for asymptomatic infection. Whether vaccinated people can still catch and spread the virus without developing the disease themselves is still being studied, Neuzil says.

As researchers continue to follow participants in the vaccine trials, they should learn more about whether vaccinated people can spread the virus, she says.

After I Get a Vaccine, Can I Stop Social Distancing and Wearing a Mask?

No. Eventually, as more people are vaccinated, this will change. But because we don’t yet know whether being vaccinated will prevent you from spreading the coronavirus, measures such as social distancing and wearing a mask will still be important even after you get vaccinated, according to the CDC.

Will a Vaccine End COVID-19?

Researchers hope that vaccination campaigns will be sufficient to end the pandemic, Neuzil says, once there is sufficient vaccine supply and enough people get vaccinated. However, Offit at the Vaccine Education Center cautions that the whole world will need to have access to these vaccines for the disease threat to be fully eliminated. If the disease is still spreading somewhere, it could always reemerge, especially if people’s immunity wanes.