The news came in lockstep with a joint statement from the Food and Drug Administration and the Centers for Disease Control and Prevention, which advised fully vaccinated people “do not need a booster shot at this time.”
“We are prepared for booster doses if and when the science demonstrates that they are needed,” the agencies said in a joint written statement.
But vaccine makers say the time could be coming as the Delta variant — first discovered in India — appears far more contagious than other strains. It’s already the most prevalent U.S. Covid strain. Pfizer/BioNTech, Moderna (MRNA) and AstraZeneca (AZN) are all testing out booster shots.
Pfizer, BioNTech Take On Delta, Vaccine Stocks Pop
At six months, Pfizer and BioNTech’s vaccine was 91.3% effective against symptomatic Covid-19, the companies said in April. It was also 95.3%-100% effective against severe disease, depending on the definition of severe disease.
But that effectiveness could be dropping off, Israel’s Ministry of Health said this week. In a real-world study, the Pfizer-BioNTech vaccine was just 64% effective against symptomatic Covid. The vaccine continues to be highly effective, 93%, against hospitalizations and deaths.
The decline in effectiveness coincides with the spread of the Delta variant and the end of social-distancing restrictions in Israel, Reuters reported.
In a study published in Nature, a single dose of the Pfizer/BioNTech and AstraZeneca vaccines “barely” protected against the Delta variant. Two doses generated an immune response in 95% of people. But antibody levels were three to five times lower against Delta than the Alpha strain.
Vaccine stocks Pfizer and BioNTech are taking two approaches. The companies testing a third dose of their original shot as a booster against the Delta variant. They also hope to begin studies in August of a Delta-specific vaccine.
The companies believe a third dose of their vaccine might be needed within six to 12 months of full vaccination.
“While protection against severe disease remained high across the full six months, a decline in (effectiveness) against symptomatic disease over time and the continued emergence of variants are expected,” they said.
But the FDA and CDC say they need a “science-based, rigorous process to consider whether or when a booster might be necessary.”
The process accounts for laboratory data, including those from pharmaceutical companies, “but does not rely on those data exclusively.”
Follow Allison Gatlin on Twitter at @IBD_AGatlin.
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