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Safeway pharmacist Ashley McGee fills a syringe with the Pfizer COVID-19 booster vaccine at a vaccination booster clinic on October 1, 2021 in San Rafael, California.
Justin Sullivan | Getty Images
The effectiveness of Pfizer and BioNTech’s Covid-19 vaccine against infection plummets over several months, from a peak of 88% one month after receiving the two-shot series to 47% six months later, study finds observational published Monday in the peer-reviewed journal The Lancet.
As the effectiveness of the two-dose mRNA vaccine against infection wanes, its protection against Covid-related hospitalizations persists, remaining 90% effective for all coronavirus variants of concern – including delta – for at least six months , according to the study, which was funded by Pfizer.
The results confirm the first reports from the Centers for Disease Control and Prevention and Israeli health officials who found that protection against infection worsened over several months, even though its effectiveness in keeping people out of hospital was delayed. .
“Protection against infection wanes in the months following a second dose,” said Dr. Sara Tartof, epidemiologist at Kaiser Permanente and lead author of the study. Kaiser Permanente conducted the research with Pfizer.
The published data comes less than two weeks after U.S. health regulators approved the distribution of Pfizer-BioNTech booster shots to a range of Americans, including the elderly and other adults deemed to be at high risk. Only a limited number of beneficiaries who initially received Pfizer’s vaccines are currently eligible to receive boosters. The new policy will make third doses of Pfizer available to about 60 million people, of which 20 million were immediately eligible, President Joe Biden said late last month.
A key Food and Drug Administration advisory committee is set to hold a two-day meeting next week to discuss whether health regulators should recommend booster shots for those who have received the Moderna or Johnson vaccines. Johnson.
Booster shots have been a controversial topic for scientists – inside and outside of government – especially since many people in the United States and other parts of the world have yet to receive them. even one dose of vaccine.
The results released Monday night were based on more than 3.4 million electronic health records from the Kaiser Permanente Southern California healthcare system between December 4 and August 8. During the study period, the proportion of positive cases attributed to the delta variant increased from 0.6% in April to almost 87% in July.
The researchers found that the effectiveness of the Pfizer vaccine against delta variant infections was 93% one month after the second dose and dropped to 53% four months later. In comparison, the efficacy against other non-delta variants was 97% after one month and declined to 67% after four months, according to the study.
The efficacy against delta-related hospitalizations remained high at 93% for the duration of the study period, the researchers said.
The decline in efficacy against infection is “most likely due to a decrease and not to a delta or other variants beyond vaccine protection,” said Pfizer’s chief medical officer for vaccines, Dr. Luis Jodar.
“Our variant-specific analysis clearly shows that the BNT162b2 vaccine is effective against all current variants of concern, including delta,” he said in a statement released alongside the study.
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