Pfizer COVID-19 booster shot extends strong protection, company says, vaccine being updated to target Delta variant
Karen Weintraub | USA TODAY
A booster shot of the COVID-19 vaccine made by Pfizer and BioNTech strongly extends protection, a new study from the companies shows, and they are developing a vaccine targeted directly at the Delta variant, which first arose in India.
The companies say they have demonstrated that a third dose of their vaccine, given six months after the second, increases neutralizing antibodies five to tenfold against the original virus and the so-called Beta variant, which was first identified in South Africa. The booster was also found to be safe.
They plan soon to publish this data and submit it to the Food and Drug Administration.
Because two doses of their vaccine appears to be effective against the Delta variant, the companies said they expect a third dose also would extend protection against it. The highly contagious variant now accounts for just over half the COVID-19 cases in the United States, according to the Centers for Disease Control and Prevention .
"Pfizer and BioNTech are conducting tests to confirm this expectation," according to a news release issued late Thursday.
Protection against severe disease remained strong during those six months, but effectiveness against severe disease began to decline toward the end, the companies said. That, plus the arrival of new variants, "are key factors driving our belief that a booster dose will likely be necessary to maintain highest levels of protection," the new release concluded.
Neither the companies nor the government recommend booster shots yet, until their safety and effectiveness can be fully explored.
The companies are also updating their vaccine, called BNT162b2, to directly address the Delta variant. They are currently producing material for a clinical trial, which they expect to begin in August, pending regulatory approvals.
Olivier Schwartz, head of the Virus and Immunity Unit, at Institut Pasteur in Paris, published a scientific article Thursday , showing that two doses of the Pfizer-BioNTech
"The vaccines are good," he said, likely including Moderna's and the single-dose Johnson & Johnson vaccine, which was also recently shown to be effective against the Delta variant. But it's not clear how long that protection will last.
Neutralizing antibodies needed to fight the virus decline substantially by one year after a natural infection, he said. Someone who was infected and then receives a single shot increases their antibody levels 100- to 1,000-fold, he said. "If you have already been infected during the first wave, receiving one dose of vaccine is very efficient," he said.
The Delta variant has rendered ineffective a treatment made by Lilly, known as a monoclonal antibody cocktail, Schwartz' study showed. The Food and Drug Administration recently removed authorization for that treatment, although a similar one, made by Regeneron, remains available and effective, he said.
Contact Karen Weintraub at kweintraub@usatoday.com.
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