Pfizer says third dose of vaccine boosts protection, including against delta variant
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Pfizer disclosed data Wednesday showing that a booster dose of its COVID-19 vaccine provides added protection beyond the currently recommended two doses, including against the delta variant.
The data, which have not been peer-reviewed, were included in a second-quarter earnings report.
Also Wednesday, researchers reported “a gradually declining trend” in the vaccine’s efficacy, from more than 96% in the first 2 months to under 84% at 6 months, according to a preprint study funded by Pfizer and BioNTech that also has not been peer-reviewed.
The usefulness of COVID-19 vaccine boosters has been debated. Earlier this month, after Pfizer and BioNTech announced positive initial findings supporting a booster dose and indicated that they would soon seek an emergency use authorization for one, CDC and FDA officials released a joint statement saying that a booster program for COVID-19 vaccines is not yet necessary, and that fully vaccinated people are protected against serious illness from all SARS-CoV-2 viruses including the variants.
“We continue to review any new data as [they become] available and will keep the public informed,” the CDC and FDA said in that statement. “We are prepared for booster doses if and when the science demonstrates that they are needed.”
According to the data in the Pfizer earnings report, neutralization titers against the delta variant in people aged 18 to 55 years who received a third dose of the Pfizer-BioNTech vaccine after 6 months were more than five times higher than after the second dose. Additionally, among older adults aged 65 to 85 years, titers against delta after were more than 11 times higher after a third dose than after a second dose.
Data from the report also showed that titers were five to eight times higher against wild-type SARS-CoV-2 and 15 to 21 times higher against the beta variant.
The new study published on the preprint server medRxiv reported 6-month findings from an ongoing study of more than 46,000 participants aged 12 years or older who received either two doses of the Pfizer-BioNTech vaccine or placebo.
According to the results, the vaccine’s efficacy peaked at 96.2% between 7 days and 2 months after the second dose, then declined to 90.1% between 2 and 4 months and 83.7% between 4 and 6 months.
“Ongoing follow-up is needed to understand persistence of the vaccine effect over time, the need for booster dosing, and timing of such a dose,” the researchers wrote.
References:
Pfizer. Second quarter 2021 earnings teleconference. July 28, 2021. https://s21.q4cdn.com/317678438/files/doc_financials/2021/q2/Q2-2021-Earnings-Charts-FINAL.pdf. Accessed on July 28, 2021.
Thomas SJ, et al. medRxiv. 2021;doi:10.1101/2021.07.28.21261159.
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Pfizer. Second quarter 2021 earnings teleconference. July 28, 2021. https://s21.q4cdn.com/317678438/files/doc_financials/2021/q2/Q2-2021-Earnings-Charts-FINAL.pdf. Accessed on July 28, 2021.
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