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Every Covid-19 Vaccine Question You’ll Ever Have, Answered

Clear guidance on everything you want to know about the vaccine (and then some)

This FAQ will be frequently updated and added to as the vaccine process continues. If you have a question that isn’t answered here, please let us know by commenting on this story, and we’ll consider it for our next update.

Exactly 272 days after the World Health Organization declared Covid-19 a global pandemic, 90-year-old Margaret Keenan and 81-year-old William Shakespeare in the United Kingdom became the first two people in the world to receive a thoroughly tested Covid-19 vaccine. (Yes, China and Russia began vaccinating people much earlier, but it’s not clear how well-tested those vaccines are.) In fact, the race for a Covid-19 vaccine began less than two weeks after the world outside China learned of the disease, when the genetic sequence of the SARS-CoV-2 virus was published on January 11.

Now two vaccines are awaiting a decision from the U.S. Food and Drug Administration (FDA), and four others in the U.S. are in phase 3 trials, the final phase before a vaccine is submitted for approval. It’s been a whirlwind, but the next whirlwind is just beginning: actually getting vaccines to the public. The U.S. will need enough doses to vaccinate about 300 million people, estimated Saad Omer, PhD, MBBS, director of the Yale Institute for Global Health, which means 600 million doses if all the vaccines ultimately approved require two doses. As countless public health experts have said throughout the pandemic, vaccines don’t save lives — vaccinations do.

“The coming Covid-19 rollout will mark the first-ever attempt to vaccinate the entire population of the United States,” said Amber Cox, PhD, director of Public Health Epidemiology at Maximus Public Health, a private company that partners with local, state, and federal governments to coordinate and deliver health services. “Moreover, this effort is taking place against the backdrop of deep political, social, and economic divisions that have challenged the public’s trust in the government and in the public health community’s response to Covid-19. A wary public will have questions — lots of them.”

So Elemental has set to answering those questions — lots of them. Keep in mind, however, that many of the answers are unknown or aren’t definitive. Uncertainty is an inherent part of scientific inquiry and the scientific process, just as it’s an unavoidable part of finding our way through a pandemic and vaccinating more people at one time than in our nation’s history.

In fact, public health officials are already trying to prepare folks to expect some level of confusion and change.

“As soon as these things start rolling out, we need to anticipate there’s going to be confusion,” said R. Alta Charo, JD, a professor of law and bioethics at the University of Wisconsin, Madison. “It’s going to be incredibly important there’s a single clear message at the federal level about what steps they are taking and what steps come next. At the state level, officials have to be really open and transparent about why some groups go first and another doesn’t, how they’re making these decisions, and then, crucially, that these are not fixed in stone, that these will change as new vaccines come online, with different profiles for risk and benefit for different groups as we see outbreaks here and there. Change doesn’t mean we were wrong, it means we’re adapting on the fly, as the situation changes, which is what a responsible health department would do.”

The biggest challenges to the Covid-19 vaccine rollout, Cox said, are trust in institutions, perceived safety of the vaccine, real safety of the vaccine, and access to the vaccine. Elemental has attempted to address all four of those issues and more in the answers below.

Throughout the answers, we frequently refer to different phases of trials, so if you’re unfamiliar with the differences, it may help to read this explainer first. In short, phase 1 trials enroll a small number of healthy people to test whether a vaccine appears initially safe and induces an immune response. Phase 2 enrolls more people and looks at safety and dosing. Phase 3 involves tens of thousands of people and looks at safety and the vaccine’s effectiveness against the actual disease. For other vaccine-related terms and acronyms you may not know, there’s a glossary at the end


  • Edward Belongia, MD, director of the Center for Clinical Epidemiology & Population Health at Marshfield Clinic Research Institute, Marshfield, Wisconsin
  • Maria Elena Bottazzi, PhD, associate dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of Texas Children’s Hospital Center for Vaccine Development, Houston, Texas
  • Noel Brewer, PhD, professor of health behavior at the University of North Carolina Gillings School of Global Public Health, Chapel Hill, North Carolina
  • R. Alta Charo, JD, professor of law and bioethics at the University of Wisconsin, Madison
  • Amber Cox, PhD, director of Public Health Epidemiology at Maximus Public Health, Reston, Virginia
  • Devon Greyson, PhD, assistant professor of communication at University of Massachusetts, Amherst
  • Margaret “Peggy” Hamburg, MD, former commissioner of the U.S. Food and Drug Administration
  • Matthew Memoli, MD, director of the Laboratory of Infectious Diseases Clinical Studies Unit at the National Institute of Allergy and Infectious Diseases, Bethesda, Maryland
  • William Moss, MD, executive director of the International Vaccine Access Center and professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland
  • René Najera, PhD, an associate in the epidemiology department of the Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland
  • Paul Offit, MD, director of the Vaccine Education Center and professor of pediatrics at Children’s Hospital of Philadelphia
  • Saad Omer, PhD, MBBS, director of the Yale Institute for Global Health, New Haven, Connecticut
  • Dorit Reiss, PhD, professor of law at the University of California Hastings Law School

Editorial note: Quotes from R. Alta Charo, Michele Andrasik, and Margaret “Peggy” Hamburg are from a SciLine webinar. William Moss and Rupali J. Limaye spoke during a Johns Hopkins Bloomberg School of Public Health media webinar briefing. Paul Offit and Noel Brewer spoke during a webinar from the American Public Health Association, and C. Buddy Creech spoke during a webinar of the Infectious Disease Society of America.

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