A study ran by the U.K. government found that the efficacy of Pfizer's Covid vaccine against the Delta variant dropped over time.
Robyn Beck/AFP via Getty ImagesThe protections offered by Pfizer’s Covid-19 vaccine against the Delta variant of the virus that causes Covid-19 drop over three months, according to a study published Thursday by scholars at Oxford University in England.
The study, which hasn’t been peer reviewed, was run by the U.K. government and examined data collected by a large-scale survey of hundreds of thousands of randomly chosen households in the country who were tested for Covid-19 beginning in November. The period in which Delta was dominant in the U.K. began in the middle of May.
The authors of the study wrote that the efficacy of AstraZeneca’s (ticker: AZN) vaccine was lower than Pfizer’s (PFE) when Delta was dominant, but the efficacy of the Pfizer vaccine dropped over time, and the authors estimated that the two vaccines will be similarly effective against Delta four to five months after receiving a second dose.
“The dynamics of protection varied over time from second vaccination, and by vaccine type, with initially larger effectiveness with [Pfizer’s vaccine] than [AstraZeneca’s], which then become more similar by ~4-5 months due to more rapid waning of effectiveness with [Pfizer’s], particularly against infections with [high viral loads] or symptoms,” the authors wrote. Write to editors@barrons.com
According to a report on the study published Thursday in Bloomberg, the observed efficacy of the Pfizer vaccine against high viral burden infections was 92% after 14 days and 78% after 90 days.
Pfizer didn’t immediately respond to a request for comment on the study.
The study also found that people infected with Delta who had received any vaccine had similar peak levels of virus as infected people who had not been vaccinated. That has “potential implications for onward transmission risk,” the authors wrote.
“SARS-CoV-2 vaccination still reduces new infections, but effectiveness and attenuation of peak viral burden are reduced with Delta,” the authors wrote.
The study comes a day after federal health officials in the U.S. announced a plan to offer booster doses to Americans beginning in late September. The U.K. is also considering a booster program, though the World Health Organization’s director general has slammed the administration of boosters by wealthy nations.
“The divide between the haves and have-nots will only grow larger if manufacturers and leaders prioritize booster shots oversupply to low and middle-income countries,” said director general Dr. Tedros Adhanom at a press conference on Wednesday.
In a statement issued through Oxford, Dr. Koen Pouwels, one of the U.K. study’s authors, said the study’s findings showed that testing remains important to stem the transmission of the virus. “Whilst vaccinations reduce the chance of getting Covid-19, they do not eliminate it,” Pouwels said. “More importantly, our data shows the potential for vaccinated individuals to still pass Covid-19 onto others, and the importance of testing and self-isolation to reduce transmission risk.”
The authors wrote their finding that vaccinated people have similar peak levels of virus as unvaccinated people implied a need for vaccinating as many people as possible.
“Those not vaccinated may not be protected by as substantial reductions in transmission among the immunized population as seen other infections, making herd immunity likely unachievable for emerging variants and requiring efforts to protect individuals themselves,” the authors wrote.
Write to Josh Nathan-Kazis at josh.nathan-kazis@barrons.com
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August 19, 2021 at 08:14PM
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Pfizer Vaccine's Efficacy Against Delta Variant Drops After Three Months: Study - Barron's
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