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Pfizer and Moderna Seek Authorization of a Fourth COVID-19 Shot. Will You Need One?

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Key Takeaways

  • Pfizer is asking for an FDA authorization of a fourth COVID-19 vaccine dose for older adults.
  • Moderna is also seeking FDA authorization of a fourth shot, but for all adults.
  • Data from Israel showed a fourth dose increased antibody levels to “slightly” higher than those achieved after three shots.

Pfizer is asking the Food and Drug Administration (FDA) to authorize a fourth shot of its COVID-19 vaccine for people 65 and older. As the vaccine manufacturer awaits the FDA’s decision, questions remain about the effectiveness of a second booster and whether it is necessary right now.

“There are reasonable arguments on both sides,” Ali Khan, MD, MPP, FACP, executive medical director of Oak Street Health, told Verywell. “If I think about this from a high level of prudence and trying to protect the patients that are structurally marginalized in so many different ways, the ultimate necessity of a fourth [shot] is not surprising to me.”

Oak Street specializes in caring for older adults and Medicare beneficiaries, many of whom are people of color or in marginalized communities.

Moderna also filed for an FDA authorization of a fourth shot of its COVID-19 vaccine for all adults, a broader request than Pfizer’s.

If the fourth shots are authorized, the rollouts might depend on White House funding. Federal officials said the Biden administration currently lacks the funds to support a second booster rollout for all Americans.

Risk of COVID-19 Among Older Adults

Entering the third spring of the pandemic, COVID-19 cases, hospitalizations, and deaths appear to be declining and plateaued in the United States. But as the Omicron BA.2 variant grows in prominence among new infections, experts are worried that the highly transmissible strain could jolt trends upward in coming weeks.

Despite a decline in cases, older adults and immunocompromised are among the most vulnerable to COVID-19. As of February, people 65–74 years old are four times more likely to be hospitalized for COVID-19 than those adults younger than 30, and 65 times more likely to die from the virus, according to the Centers for Disease Control and Prevention (CDC). The risks are even greater for people 75 years and older.

CDC data from January showed that unvaccinated adults aged 65 and above faced 15 times the risk of a COVID-associated hospitalization than others in the same age group who had been fully vaccinated and boosted.

Will a Fourth Dose Be Effective?

The mRNA booster can persist against the Omicron variant for at least four months, according to a February CDC study. Based on that timeline, those who received their shot at the beginning of the booster rollout, in November 2021, may have lower levels of protection by now.

Whether a second mRNA booster will restore antibodies significantly is unclear. The bulk of the data on fourth doses comes from Israel, where a recent study found that a fourth dose of either Pfizer or Moderna increased people’s antibody levels to “slightly” higher than those achieved after the third shot.

The study used a cohort of only 1,050 healthcare workers, 274 of whom received a fourth dose from either Pfizer or Moderna. The researchers noted that this was too small a cohort to accurately determine the fourth shot’s efficacy. Further, older adults were not included in the study.

Still, based on study results, a fourth dose of the Pfizer vaccine was 30% effective against any COVID-19 infection and 43% effective against symptomatic infection. The Moderna vaccine fared worse, with an 11% efficacy against any COVID-19 infection and 31% efficacy against symptomatic infection. Had the study sample been larger, the efficacy against symptomatic infection could be 65% at most, according to the researchers.

Maximum vaccine efficacy appears to be achieved through three doses of an mRNA vaccine, thus the purpose of a fourth dose would be to restore antibody levels, the researchers wrote. They added that the fourth dose was “immunogenic, safe, and somewhat efficacious,” with little difference between the two vaccines.

What Are Healthcare Providers Saying?

It will be important for providers to have clear, transparent conversations with patients about a fourth shot if it is authorized, Khan said. This includes reminding people that the vaccines work best against hospitalizations and death, he added.

“We’re recognizing, especially in primary care, that this is a journey, which we’re all learning together,” Khan said.

Khan added that he will not be surprised if a fourth shot is authorized for older adults, but that he is awaiting CDC guidance before determining if it is necessary. It’s hard to interpret Israel’s current data on the fourth shot’s effectiveness, he said.

“In the background, we’re preparing our patients for the potential of the fourth booster and starting to pair that with a message of, ‘this starts to become like your annual flu shot,’” Khan said.

Regardless of an FDA authorization, it is important for patients to take precautionary measures against the virus, as “cases can skyrocket so quickly,” Khan said. That includes wearing a well-fitted mask, staying in well-ventilated areas or outdoors when possible, and getting tested when necessary. Even for those who do not feel at risk in their current community, it can be a good idea to prepare for the future by purchasing some at-home tests or extra masks, he added.

“Continue to keep yourself safe, particularly for seniors, as we face what is out there–be that BA.2 or whatever else is around the corner,” Khan said.

What This Means For You

The FDA will meet to decide whether or not to authorize a fourth dose of the Pfizer vaccine for adults 65 and older on April 6.

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4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Risk for COVID-19 infection, hospitalization, and death by age group.

  2. Centers for Disease Control and Prevention. COVID data tracker.

  3. Ferdinands JM, Rao S, Dixon BE, et al. Waning 2-dose and 3-dose effectiveness of mRNA vaccines against COVID-19–associated emergency department and urgent care encounters and hospitalizations among adults during periods of Delta and Omicron variant predominance — VISION Network, 10 states, August 2021–January 2022. MMWR Morb Mortal Wkly Rep. 2022;71(7):255-263. doi:10.15585/mmwr.mm7107e2

  4. Regev-Yochay G, Gonen T, Gilboa M et al. Efficacy of a fourth dose of Covid-19 mRNA vaccine against OmicronN Engl J Med. Published online March 16, 2022. doi:10.1056/nejmc2202542