Q: Who is making the vaccines?

A: The vaccines are made by different companies: One is being developed by pharmaceutical giant Pfizer and its German partner, BioNTech, and the other by biotechnology firm Moderna, in partnership with the National Institute of Allergy and Infectious Diseases. Both drugmakers have moved at record speed and will seek regulatory clearance for their vaccines in the coming weeks.

Q: What will happen next?

A: Companies will apply to federal regulators for authorization to provide the vaccines more broadly. FDA regulators will review the effectiveness, safety and manufacturing of each vaccine. An FDA advisory committee will vote on whether to recommend that the agency greenlight each vaccine.

In December:

– The FDA may authorize one or both vaccines.

– One or two days later, a Centers for Disease Control and Prevention advisory committee will discuss prioritizing vaccines for high-risk groups.

End of 2020:

– The government projects that Pfizer and Moderna will provide 40 million doses, enough for 20 million people, by the end of the year.

Q: When will I be able to get vaccinated?

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A: That depends on your job, your age and your health.


The vaccines could begin to be distributed as soon as late December to those in high-risk groups – an estimated 200 million people – who will receive priority, according to a framework devised by an advisory committee to the Centers for Disease Control and Prevention. Government officials said that if both vaccines are authorized, they anticipate having enough doses for 20 million people by year’s end.

The exact criteria for who will be first in line will be defined immediately after a vaccine is authorized, but the general principles have been discussed for months. You may qualify for earlier access because of your job: Health-care workers and first responders are likely to be among those prioritized. People who have essential jobs, such as teachers and food workers; those who are at higher risk because of their age; and those who have underlying conditions that increase their risk for severe disease are also likely to receive earlier access.

Healthy younger adults who don’t have medical conditions or high-risk jobs are likely to begin to get vaccinated starting in April, but not everyone will be able to get the shots immediately. And children aren’t even included in most coronavirus vaccine trials – Pfizer is the first company to expand its trial to people 12 and older – so they probably will be among the last to get access.

“I would say starting in April, May, June, July – as we get into the late spring and early summer – that people in the so-called general population, who do not have underlying conditions or other designations that would make them priority, could get” shots, said Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases.

Q: How will the vaccines be shipped?

A: The Moderna vaccine is stored frozen at minus-20 degrees Celsius, but it keeps for a month at refrigerator temperatures. This could make it easier to distribute to pharmacies and to rural areas that don’t have specialized freezers.

The vaccine from Pfizer and BioNTech must be kept at an ultracold, minus-70 degrees Celsius. The company has created its own GPS-tracked coolers filled with dry ice to distribute it.


Each vial of the Pfizer vaccine holds five doses when diluted. Once thawed, the undiluted vial can be kept in a refrigerator for only five days. A diluted vial can be kept for only six hours before it must be discarded.

Q: How many doses will I need?

A: Both vaccines require two doses. Pfizer’s booster shot will be given three weeks after the first one; Moderna’s is spaced four weeks later.

Q: How do the vaccines work?

A; If cleared, these two will be the first vaccines using messenger RNA technology ever approved for human use by the Food and Drug Administration. It is different from more traditional vaccines, which often use a weakened or dead version of a virus, or a laboratory-generated protein. Both vaccines use a snippet of the virus’s genetic code to instruct cells to build the spike protein on the surface of the coronavirus, teaching the immune system to recognize the real thing.

Q: How were the vaccines made so fast?

A: Historically, vaccines have taken years to develop. Before these, the mumps vaccine – which took four years to develop – was the fastest to be approved for use in humans. Developing messenger RNA vaccines has been fast because scientists were able to start their work before there was a known case of the novel coronavirus in this country, using the viral genome shared online as a template. Making messenger RNA vaccines does not require time-consuming steps, such as growing ingredients in chicken eggs.

Q: Are the vaccines safe?

A: The full safety data haven’t been made available yet, but no serious safety concerns have been reported in either trial. Intensive safety monitoring will continue after the vaccines begin to be used. The side-effects profile of the Pfizer vaccine includes pain at the injection site, as well as fatigue, chills and fever. The side effects noted in Moderna’s news release include pain at the injection site, muscle aches and headaches.

Q: Should I still get vaccinated if I already had the coronavirus?


A: We are still learning how long immunity to the coronavirus lasts, after an infection or a vaccination. Typically, an infection causes better immunity than a vaccine, but not always – the vaccines for tetanus and human papillomavirus, for example, offer better protection than recovering from a natural infection.

The coronavirus vaccine trials did not exclude people who already had been infected, and the full data from those trials may help reveal how the vaccine performed in those people. Until the CDC committee evaluates the full data on any authorized vaccine, the agency won’t make recommendations about whether people who already were infected should receive it.

Q: How much will the vaccines cost?

A: The federal government has pre-purchased hundreds of millions of vaccine doses with taxpayer money, and vowed to make them available free.

Q: Could I be mandated to get the vaccine by my employer?

A: That’s not likely anytime soon. Vaccines authorized under the FDA’s emergency authority, as these will be at the start, cannot be mandated, said Beth Bell, a member of the federal advisory panel on immunizations that will be making recommendations to the CDC on who should get the first doses. There also won’t be enough vaccine for everyone for months. Many employers offer flu vaccines to their employees, but such programs are voluntary in most settings except hospitals.

Eventually, the vaccines probably will be approved under the FDA’s more lengthy licensure rules and will no longer be considered experimental. But even then, requiring a coronavirus vaccine as a condition for returning to the factory floor or office or retail showroom would create the potential for conflicts, said Jennifer B. Rubin, a labor lawyer at the law firm Mintz in San Diego.


“It’s going to create some really interesting political and legal issues about the haves and have-nots,” she said. “What about people working at fast-food restaurants, servers, people who staff gyms? There’s going to be a need for guidance under the circumstances for employers.”

Q: Will I still need to socially distance?

A: Yes. Even after a vaccine is approved, experts say people will need to wear masks and socially distance – in part because the vaccine doses will be limited, and it will take time to immunize enough of the population to stop the virus from spreading. Experts say the return to normalcy could take many months or longer.

Q: What will happen if I don’t get vaccinated?

A: Two other vaccines are in the final phase of testing in the United States, and those trials are also moving much faster than expected because of surging coronavirus cases. Two more are expected to begin soon. Later-generation vaccines are also still in development.

The goal is to immunize enough people to achieve herd immunity, when enough people are immune that a disease can no longer spread. The number of people who need to be immunized to reach that milestone will depend on how effective the vaccines are – a factor that won’t be clear until the trials have finished.

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The Washington Post’s Lena H. Sun and Christopher Rowland contributed to this report.