A booster shot of Pfizer’s COVID-19 vaccine provides strong protection, at least initially, against COVID-19 hospitalization, although the effect against the Omicron virus variant is lower than that seen when the Delta strain was prevalent, according to a new study.
Researchers in Qatar estimated that the booster was 76.5 percent effective against severe, critical, or fatal COVID-19 caused by the Omicron variant as compared to the protection offered by the two-dose primary series.
The effectiveness was measured relatively soon after administration, with a median follow-up time of 22 days in the booster cohort and 21 days in the nonboosted group.
“Having a booster recently is very protective against COVID-19 hospitalization and death due to Omicron,” Dr. Laith Abu-Raddad, one of the researchers, told The Epoch Times in an email.
The study was published by the New England Journal of Medicine following peer review.
The study team also looked at the effectiveness of a booster of Moderna’s shot but couldn’t ascertain how well it worked against severe, critical, or fatal COVID-19 because none of these types of cases were recorded in the booster group and only three were recorded in the nonboosted cohort.
However, they found that both the Pfizer and Moderna boosters provided little protection against infection from Omicron, a variant of the CCP (Chinese Communist Party) virus, or SARS-CoV-2.
Pfizer’s booster was estimated at just 49.4 percent effective at preventing infection compared to the primary series and Moderna’s was pegged at 47.3 percent. U.S. regulators and the World Health Organization say the efficacy threshold is 50 percent for a successful vaccine.
“Against earlier variants such as Delta we had much better protection, greater than 80 percent,” said Abu-Raddad, a professor and epidemiologist at Weill Cornell Medicine–Qatar.
“This suggests that we need to start thinking about developing a new generation of vaccines with high protection against a broad range of variants and an effectiveness that does not wane rapidly.”
The study was funded by Well Cornell Medicine–Qatar and the Qatari government, among other institutions.
Limitations include the lack of an estimate of the Moderna booster’s effectiveness against COVID-19-related hospitalization and death.
The study population was everybody who received a primary series of the Pfizer or Moderna vaccine in Qatar between January 2021 and January 2022. People who were documented as recovering from a COVID-19 infection, known as natural immunity, before the start of follow-up were excluded. That’s because there was concern that the presence of natural immunity may affect the protection from boosters, the researchers said, citing one of their previous studies.
Abu-Raddad has also led research on natural immunity in Qatar, including a study that found that natural immunity protects well against severe, critical, or fatal COVID-19 cases caused by Omicron.
Natural immunity protects better than the vaccine boosters against the Omicron and Delta variants, according to new and previous studies.
Some research and real-world data, including surveillance data from the United Kingdom (pdf), indicates that the protection from boosters wanes, especially against infection. That has prompted authorization of a second booster in some countries; Pfizer announced recently that it will seek clearance in the United States for an additional shot.
“We will continue to follow these vaccinated cohorts to see how the effectiveness of the booster shot will wane over time,” Abu-Raddad said.