Real-world data from Israel confirmed that a booster dose of the BNT162b2 vaccine is highly protective against death due to Covid-19 and progression to severe disease.
A study involving more than 800,000 people age 50 years and older showed a 90% lower risk for death from Covid-19 among people receiving a booster dose at least five months after a second dose of the BNT162b2 vaccine, compared to fully vaccinated people who did not receive a booster.
In another study evaluating outcomes among close to 4.7 million people who received two doses of the BNT162b2 vaccine, a third booster dose was associated with a significantly lower rate of infection and severe illness.
Findings from both studies were published online Dec. 8 in The New England Journal of Medicine.
Israel implemented a nationwide Covid-19 vaccine booster campaign in late July as the 4th wave of the virus—prompted by the emergence of the Delta SARS-CoV-2 variant—was spiking in that country. Although a third dose was initially recommended only for people age 60 years and older, health officials later expanded the booster campaign to include younger age groups who had received a second BNT162b2 dose at least five months earlier.
The population study included data from the Israel Ministry of Health database on 4,696,865 people 16 years of age or older.
“Although observational studies suggest that the booster dose is effective against both confirmed infection and severe disease in the elderly population, the extent of protection of an additional dose in younger age groups requires further clarification,” wrote researcher Yinon Bar-On, MSc, of Technion-Israel Institute of Technology, Haifa, Israel, and colleagues.
In their primary analysis, the researchers compared the rates of confirmed Covid-19 infection, severe illness, and death among people receiving a booster dose of BNT162b2 at least 12 days earlier with rates among people who did not receive a third dose of the vaccine.
In the secondary analysis, the researchers compared these outcomes among the booster group to rates experienced by people receiving a booster dose three to seven days earlier (early post-booster group).
“The rate of confirmed infection was lower in the booster group than in the non-booster group by a factor of approximately 10 (range across five age groups, 9.0 to 17.2) and was lower in the booster group than in the early post-booster group by a factor of 4.9 to 10.8,” Bar-On and colleagues wrote.
The adjusted rate difference ranged from 57.0 to 89.5 infections per 100,000 person-days in the primary analysis and from 34.4 to 38.3 in the secondary analysis, and the rates of severe illness in the primary and secondary analyses were lower in the booster group by a factor of 17.9 (95% CI, 15.1-21.2) and 6.5 (95% CI, 5.1- 8.2), respectively, among those 60 years of age or older and by a factor of 21.7 (95% CI, 10.6 to 44.2) and 3.7 (95% CI, 1.3 to 10.2) in people age 40 to 59 years.
The adjusted difference in the rate of severe illness between the non-booster and booster groups was 5.4 cases per 100,000 person-days among those 60 years and older and 0.6 cases per 100,000 person days among those 40 to 59 years of age.
In the secondary analysis, the rate of severe illness 12 or more days after the booster was lower than the rate three to seven days after the booster by a factor of 6.5 (95% CI, 5.1-8.2) among those age 60 years and older, and by a factor of 3.7 (95% CI, 1.3-10.2) among those age 40 to 59 years.
“The rate of severe disease in the youngest age groups (16 to 29 and 30 to 39 years of age) was very low, and there were not enough cases to estimate the rate ratio reliably,” the researchers wrote.
A second study, also published Dec. 8 in NEJM, included data on 843,208 people age 50 years or older who were members of the large Israeli health provider Clalit Health Services, and who were fully vaccinated (2 doses) with the BNT162b2 vaccine at least five months earlier. Ninety percent received a booster dose of the vaccine during the 54-day study period (August 6-September 29, 2021).
A total of 65 study participants in the booster group (0.16 per 100,000 persons per day) and 137 in the non-booster group (2.98 per 100,000 persons per day) died from Covid-19.
Cox proportional-hazards regression modeling revealed that the adjusted hazard ratio for death from Covid-19, compared to the non-boosted study participants, was 0.10 (95% CI, 0.07-0.14; P<0.001), wrote researcher Ronen Arbel, PhD, of Clalit Health Services, Tel Aviv, and colleagues.
In accompanying commentary, pediatrician Minal K. Patel, MD, who is a member of the CDC’s Covid-19 Response International Task Force, wrote that the 2 studies “provide much-needed evidence of the effectiveness of the booster dose.”
Patel noted that as of late November, 107 countries had instituted booster dosing programs, while many countries continue to have low rates of initial vaccination.
“Population coverage with a full primary series is less than 10% in 45 countries and less than 40% in 105 countries,” Patel wrote. “The low current vaccination rates are largely due to limited vaccine supply in low-income countries, which is forecasted to be resolved by early 2022, although challenges will remain in ensuring that everyone is vaccinated.”
While the real-world benefits of a third Covid-19 dose are becoming clearer, Patel noted that in many countries, limited vaccine supply in the near future will continue to dictate decisions about the best use of vaccine.
She cited a cost-benefits analysis from the United States findings that 481 people would need to be vaccinated with a booster dose to prevent one hospitalization. By way of contrast, the study found that 50 people would need to be vaccinated with the initial two doses of vaccine to prevent one hospitalization.
“It is important that vaccination with the primary series, especially in high-risk populations, remain a top priority everywhere, because this will ultimately lead to a greater reduction in severe disease and death,” Patel concluded.
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Real-world data from Israel confirm that a booster dose of the BNT162b2 vaccine is highly protective against death due to Covid-19 and progression to severe disease.
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In a study evaluating outcomes among close to 4.7 million people who received two doses of the BNT162b2 vaccine, a booster dose was associated with a significantly lower rate of infection and severe illness.
Salynn Boyles, Contributing Writer, BreakingMED™
No outside funding source was disclosed for the Clalit Health Services study, and lead researcher Ronen Arbel and the other investigators reported no relevant disclosures. Editorial writer Minal K. Patel reported no relevant disclosures.
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Topic ID: 79,190,730,933,190,926,192,927,925,934
