For months, questions have lingered over when people might need boosters to keep their COVID-19 vaccines effective. The conversation took on new urgency with the arrival of the highly contagious Delta variant, even though initial studies suggest that the original shots are still working against the latest strain. But as more data has come in, the federal government has said that it is recommending booster shots based on new studies that show how protected from COVID you are after being vaccinated for months.
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During a press conference on August 18, top health officials from the Biden administration announced that it would begin offering COVID-19 booster shots beginning the week of Sept. 20 to all previously vaccinated Americans. The administration cited three separate studies released by the Centers for Disease Control and Prevention (CDC) on the same day in its weekly report as evidence in its decision. When data from the research is combined, it shows that current vaccines are about 55 percent effective against infection with the virus, 80 percent effective against symptomatic infection, and 90 percent or more effective against hospitalization as a result of COVID-19, Ellie Murray, an epidemiologist at Boston University, told The New York Times.
In one of the studies released by the CDC, state data from New York collected between May 3 and July 25 was analyzed, marking the period when the Delta variant rose to become the dominant strain of the virus. Results found that the effectiveness of the vaccines fell from 91.7 percent to 79.8 percent over the course of the study, while hospitalizations notably remained the same. The analysis also showed that about 20 percent of new cases and 15 percent of new hospitalizations from the disease were breakthrough infections reported in fully vaccinated people.
In another one of the studies, residents of 3,862 nursing homes were analyzed from March 1 to May 9 while Alpha was the dominant variant. Later, about 15,254 nursing homes were analyzed from June 21 to Aug. 1, when the Delta variant had taken over. While the study didn’t measure protection against severe illness, results found that the efficacy rates of the vaccines against COVID-19 infections overall dropped from 75 to 53 percent. The study’s authors concluded that “additional doses of COVID-19 vaccine might be considered for nursing home and long-term care facility residents.”
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The third study released by the CDC analyzed data from patients at 21 hospitals across 18 states. Results found that the vaccines were 86 percent effective against hospitalization from the virus even when the Delta variant had risen to dominance. Adults who were not immunocompromised saw even higher protection at 90 percent.
However, the release of the studies quickly fueled the arguments of some health experts against the Biden administration’s decision, with many saying that the data within them didn’t suggest additional shots would be necessary for all members of the population. “Those numbers are actually very good,” Murray told The Times, adding: “The only group that these data would suggest boosters for, to me, is the immunocompromised.”
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Others agreed with Murray’s analysis. “These data support giving additional doses of vaccine to highly immunocompromised persons and nursing home residents, not to the general public,” Celine Gounder, MD, an infectious disease specialist at Bellevue Hospital Center and a former adviser on the pandemic to the administration, told The Times.
Still, others pointed out that boosters were far from the only protection against the virus that could go a long way in keeping vulnerable portions of the population safe, such as the use of face masks and social distancing. “As we’re releasing the brakes on these other non-pharmaceutical interventions, we may see more cases,” Maria Sundaram, PhD, an infectious-disease epidemiologist at the University of Toronto Dalla Lana School of Public Health, told The Washington Post. “Vaccines are very, very helpful, but they’re not the end-all, be-all of COVID-19 prevention.”
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