Experts Divided Over Current Need for COVID Booster Shots

Older woman receives a vaccine and doctor is placing bandaid on her arm.

Jasmin Merdan / Getty Images

Key Takeaways

  • The administration recently announced its plan to offer COVID-19 booster shots starting in September.
  • Some experts are unsure on whether there’s enough robust evidence to support the recommendation of booster shots.
  • In addition to COVID-19 vaccines and boosters, experts say there should also be greater emphasis on wearing masks, contact tracing, and improving ventilation systems.

U.S. health officials recently announced a plan to offer COVID-19 vaccine boosters to fully vaccinated adults ages 18 and older starting September 20. 

According to a joint statement by the Health and Human Services, Food and Drug Administration (FDA), Centers for Disease Control and Prevention (CDC), and others, boosters would available to Americans eight months after they received the second dose of their Pfizer-BioNTech or Moderna vaccine. The plan is awaiting approval.

The booster recommendation is based on new data from the CDC which indicates that COVID-19 protection wanes over time.

However, many experts are questioning whether there is enough evidence proving a need for boosters given that the vaccines remain effective at what they were intended to do—preventing serious disease, hospitalization, and death from COVID-19. 

Why Might COVID-19 Booster Shots Be Needed?

According to the CDC, fully vaccinated individuals are now less protected against mild and moderate COVID-19 disease due to the Delta variant. But the vaccines are still working well at preventing severe cases.

“Booster doses are needed if we see a substantial reduction in vaccine effectiveness against severe COVID-19 disease, hospitalization, and death,” William Moss, MD, executive director of the International Vaccine Access Center at the Johns Hopkins Bloomberg School of Public Health, tells Verywell. “Data on breakthrough infections resulting in hospitalization and death are available in the United States and we continue to see relatively high vaccine effectiveness against these outcomes, albeit slightly lower than was seen in the clinical trials.”

Booster shots are now being offered to “stay ahead of the virus,” even though fully vaccinated individuals still have a high degree of protection from the worst outcomes of COVID-19, Vivek Murthy, MD, MBA, U.S. Surgeon General, said at a White House press briefing.

But health officials say, for some of the groups first eligible for vaccination—older adults and immunocompromised people—that protection may be waning.

“We already have published data demonstrating poor or limited protective responses to the vaccine in certain groups who traditionally were at risk for poor responses—elderly and [those with] various immune conditions,” Stanley H. Weiss, MD, an infectious and chronic disease epidemiologist and professor at the Rutgers New Jersey Medical School and the Rutgers School of Public Health, tells Verywell.

In fact, earlier this month, the FDA authorized additional vaccine doses for immunocompromised individuals to increase their protection against COVID-19.

Vaccines Prevent Severe Cases, Not Infection

U.S. health officials say that the administration’s plan to offer booster shots this fall is rooted in science. But they're still looking at the data to confirm whether boosters are really needed as early as September.

“Further studies are in progress, and are needed, to refine our understanding,” Weiss says. “Given the high rate of breakthrough infection with Delta among fully vaccinated persons, the data does support proceeding now with these changes in policies. Alternative boosting strategies remain under study, and it will not be surprising if future innovations lead to additional changes.”

Rochelle P. Walensky, MD, MPH, director of the CDC, cited several studies at the White House briefing to demonstrate how vaccine-induced protection against the virus wanes over time, including:

  • A CDC report showing that vaccine effectiveness against infection dropped from 91.7% to 79.8%.
  • A Mayo clinic analysis—which was a preprint article and should not be used to guide clinical practice—that found that Pfizer-BioNTech and Moderna’s vaccine effectiveness against infection dropped from 76% to 42% and 86% to 76%, respectively.
  • A different CDC report demonstrated that vaccine effectiveness against infection declined over time, from 74.7% in the months of March to May to 53.1% in June to July.

Still, authorities clarified that the vaccines continue to offer the best protection against severe disease.

“The data presented by the CDC showed decreased vaccine effectiveness against infection with SARS-CoV-2 from the time period before Delta was the dominant viral variant to when it was, particularly in some populations such as residents of nursing homes,” Moss says. “However, this data also showed continued high protection against hospitalization and death.” 

Many experts point out that most of the data the CDC presented focus on COVID-19 infection, rather than hospitalization or death. The vaccines were always meant to prevent severe outcomes, not provide 100% protection against infection. The vaccines are still effective for their intended purpose.

However, health officials say this current protection against severe disease, hospitalization, and death could potentially diminish in the coming months.

“The assumption seems to be that decreased effectiveness against infection now will, over time, become decreased effectiveness against severe disease,” Moss says. “There is some data from Israel suggesting this may be the case, but I am not convinced this will be true for everyone. Perhaps just for older adults and others who are at higher risk of severe COVID-19 and have weaker immune systems.”

What This Means For You

If you are not immunocompromised you cannot receive a booster shot yet. But if you haven't been vaccinated, you can find an appointment near you here.

Solely Relying on Boosters Is Not Enough

Earlier this month, the World Health Organization (WHO) called for a moratorium on booster doses until the end of September to allow at least 10% of every country to get vaccinated first.

While high-income countries have given about 100 doses for every 100 people, low-income countries have only administered 1.5 doses for every 150 people due to lack of vaccine supply, according to Tedros Adhanom Ghebreyesus, PhD, director-general of the WHO.

“The major negative consequences are whether administration of booster doses in the United States distracts us from our primary goal of vaccinating the unvaccinated and whether such use of these vaccine doses further exacerbates global inequities in vaccine access,” Moss says. “The latter is a complex issue, but the United States and other higher-income countries need to do more to get vaccine doses to those who need them in low and middle-income countries.”

If vaccine availability does not improve in low- and middle-income countries, the virus will continue to circulate and mutate in unprotected areas, increasing the risk of more contagious variants emerging. This emphasizes the importance of increasing vaccine coverage globally, instead of focusing on certain regions or countries.

The booster shot can potentially decrease new infections, virus transmission, and slow virus spread, but it’s a serious error to rely on vaccination alone, Weiss says. He adds that greater emphasis should also be placed on some major factors like:

  • Wearing well-fitted masks
  • Conducting effective contact tracing to ensure early interaction with the medical care system
  • Improving heating, ventilation, and air conditioning systems

“The increased transmissibility of Delta means greater, not lesser, precautions needed, including greater distancing, especially inside but also outside,” Weiss says. “There remains a potential for further variants of the COVID-19 that may be even more dangerous than Delta, in terms of transmissibility and/or virulence. So far, we have lagged behind rather than stayed ahead. This pandemic remains a challenge. Letting our guards down will lead to new surges.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

8 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. U.S. Department of Health & Human Services. Joint Statement from HHS Public Health and Medical Experts on COVID-19 Booster Shots.

  2. Centers for Disease Control and Prevention. COVID-19 Vaccine Booster Shot.

  3. The White House. Press Briefing by White House COVID-⁠19 Response Team and Public Health Officials.

  4. Food and Drug Administration. Coronavirus (COVID-19) Update: FDA Authorizes Additional Vaccine Dose for Certain Immunocompromised Individuals.

  5. Rosenberg ES, Holtgrave DR, Dorabawila V, et al. New COVID-19 Cases and Hospitalizations Among Adults, by Vaccination Status — New York, May 3–July 25, 2021. MMWR Morb Mortal Wkly Rep. 2021;70:1150-1155. doi:10.15585/mmwr.mm7034e1

  6. Puranik A, Lenehan PJ, Silvert E, et al. Comparison of two highly-effective mRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalence. medRxiv. 2021. doi:10.1101/2021.08.06.21261707

  7. Nanduri S, Pilishvili T, Derado G, et al. Effectiveness of Pfizer-BioNTech and Moderna Vaccines in Preventing SARS-CoV-2 Infection Among Nursing Home Residents Before and During Widespread Circulation of the SARS-CoV-2 B.1.617.2 (Delta) Variant — National Healthcare Safety Network, March 1–August 1, 2021. MMWR Morb Mortal Wkly Rep. 2021;70:1163-1166. doi:10.15585/mmwr.mm7034e3

  8. World Health Organization. COVID-19 Virtual Press conference transcript - 4 August 2021.

By Carla Delgado
Carla M. Delgado is a health and culture writer based in the Philippines.