Now that vaccination is well underway for health care workers and residents of long-term care facilities, the debate continues about whether the next round should prioritize older people who are most likely to die of COVID-19 or frontline workers who are at greatest risk of exposure.

The Pfizer/BioNTech vaccine received emergency use authorization from the Food and Drug Administration (FDA) on December 11, followed by the Moderna vaccine a week later. As of December 23, just over 1 million people in the United States—out of a total population of about 330 million—have received their first dose of the two-shot vaccines, according to a Centers for Disease Control and Prevention (CDC) vaccination tracker.

Among them were staff members at the National Institutes of Health (NIH), which codeveloped the Moderna vaccine. NIH director Francis Collins, MD, PhD, National Institute of Allergy and Infectious Diseases director Anthony Fauci, MD, Health and Human Services Secretary Alex Azar and several NIH frontline workers were vaccinated at a publicly broadcast vaccine kickoff event on December 22. Former President Barack Obama, Vice President–elect Kamala Harris and others have said that if Fauci—the federal government’s leading voice on COVID-19—endorses the vaccine, they will consider it safe.

Azar said it is “nothing short of miraculous” to have a safe and effective vaccine within a year after the pandemic emerged. While the rapid development and rollout of the first vaccines, spearheaded by Operation Warp Speed, has been unprecedented, Azar stressed that the process is “not cutting any corners,” and the vaccines are thoroughly vetted by independent career scientists.

Vice President Mike Pence, President-elect Joe Biden and senior members of Congress, including Senate Majority Leader Mitch McConnell (D–Kentucky) and House Speaker Nancy Pelosi (D–San Francisco), also publicly received their first shots last week in a show of confidence in the safety of the vaccines.

Rep. Barbara Lee (D–Calif.) specifically encouraged African Americans, Latinos and other people of color, who are disproportionately affected by COVID-19 but tend to be skeptical of the medical field and the government, to get vaccinated.

“I urge everyone, especially people of color who have suffered the most from this pandemic, to recognize that the risk of contracting COVID-19 far outweighs the understandable skepticism of this vaccine,” Lee said as she received her own shot. “I trust it, and I hope you will too.”

Risk of Death Versus Risk of Exposure 

The day after the approval of the Moderna vaccine, the CDC’s Advisory Committee on Immunization Practices (ACIP) met to discuss the next round of vaccine prioritization after Phase 1a.

The committee is trying to balance sometimes competing goals, including reducing COVID-19 mortality, slowing transmission of the coronavirus, maintaining health care capacity, minimizing disruption to society and ensuring equity in vaccine distribution.

Some experts urge prioritizing older people, who are at much greater risk for severe COVID-19 and death. The death rate for people 85 and older is about 600 times higher than the mortality rate for people ages 18 to 29, the rate for those ages 75 to 84 is abut 200 times higher and the rate for those ages 65 to 74 is about 90 times higher, according to the CDC. People over 75 account for a quarter of COVID-19 hospitalizations.

People with underlying health conditions, including obesity, diabetes, chronic lung disease and cancer, are also at greater risk for severe COVID-19 and death.

The Pfizer/BioNTech and Moderna vaccines were 95% and 94% effective at reducing symptomatic COVID-19 in Phase III clinical trials. Reducing severe disease would relieve the pressure on intensive care units, which are stretched to the breaking point across the country.

On the other hand, prioritizing frontline essential workers would get vaccines out faster to the people at greatest risk of exposure to the coronavirus, a group that disproportionately includes low-income people, African Americans and Latinos. The incidence of new COVID-19 infection is highest among those ages 18 to 29.

Although it is not yet clear how much the vaccines will curb transmission—early data suggest they may reduce asymptomatic infection by about two thirds—doing so is crucial for resuming normal life. For example, vaccinating teachers early could allow schools to safely reopen.

In the end, ACIP recommended that both older people and frontline workers should be given priority in an effort to balance preventing illness and death from COVID-19 and preserving the functioning of society.

Phase 1a:

  • Health care workers—21 million
  • Long-term care facility residents—3 million

Phase 1b:

  • Frontline essential workers—30 million
  • People ages 75 and older—19 million not included in Phase 1a

Phase 1c:

  • People ages 65 to 74—28 million not included in earlier phases
  • People ages 16 to 64 years with high-risk health conditions—81 million not included in earlier phases
  • Other essential workers—20 million not included in earlier phases

 Phase 2:

  • All people ages 16 and older not included in Phase 1.

Although ACIP recommends prioritization for the country as a whole, states and local jurisdictions have the final say in determining who will be vaccinated next. Some states may opt to offer priority vaccine access to other at-risk groups, including homeless individuals and incarcerated people.

According to the CDC, nearly 10 million vaccine doses have been distributed as of December 23, but only about a tenth of those have actually gone into people’s arms. Each recipient will need two doses. The U.S. has contracted with Pfizer and Moderna to purchase about 200 million doses of each vaccine, but ramping up production takes time. Operation Warp Speed estimates there will be enough doses to vaccinate 20 million people in December and an additional 50 million by the end of February. FDA authorization of additional vaccines, including a single-shot candidate from Johnson & Johnson, would increase the total supply.

In the meantime, vaccines are expected to remain in short supply for months. Discussions about who should have priority are ongoing in health departments nationwide—accompanied by heated debates on social media—as advocates for seniors, people in various professions and people with specific health conditions, including cancer and HIV, lobby for their constituents to move ahead in the line. Skirmishes have already broken out around which health care workers should be vaccinated first in Phase 1a.

Based on current timelines, younger adults with no risk factors could start getting vaccinated in the spring or early summer. Most experts predict that herd immunity could be achieved after around 70% of people have been vaccinated, at which point there would be too few susceptible people for the virus to spread easily.

Until then, and until more is known about whether the vaccines prevent transmission as well as symptomatic illness and how long vaccine-induced or natural immunity will last, it is important for everyone—even those who have already been vaccinated or had COVID-19—to keep up precautions such as wearing masks and social distancing.

Click here to read the ACIP vaccine recommendations in the CDC’s Morbidity and Mortality Weekly Report.