Immunity from the COVID-19 vaccines likely to ‘wane, and not plummet,’ CDC director tells Congress

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Federal health officials told lawmakers it’s too soon to say whether vaccinated Americans will need a COVID-19 booster shot.

The delta variant, which is now thought to be the dominant strain of the virus in the U.S., is ripping through unvaccinated communities in the U.S., sending up case counts, hospitalizations, and deaths after a relatively low-key spring. The U.S. last week averaged about 26,000 cases a day, a 70% increase compared to the 7-day moving average of about 15,000 new cases the week before, according to the Centers for Disease Control and Prevention.

The more infectious variant is likely behind rare breakthrough infections among the vaccinated, which is another reason that there are increasingly louder questions about whether immunity may be waning among some people who have been vaccinated and if boosters are needed to combat declining protection.  

The booster debate has also been fueled by preliminary data out of Israel that indicates BioNTech SE
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and Pfizer Inc.’s
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shot is 64% effective against delta — a significant decline from the 95% efficacy rate reported in clinical trials. 

“We have the same data as Israel,” Sen. Richard Burr (R-N.C.) said during Tuesday’s Senate HELP committee hearing. “Why aren’t we making the same decisions?”

Dr. Anthony Fauci, chief medical adviser to President Joe Biden, later responded, saying: “Right now we are doing studies to determine whether or not we will need boosters, to increase the durability of protection. We don’t want people to believe that when you’re talking about boosters that means that the vaccines are not effective. They are highly effective. We’re talking about the durability.”

It’s still unknown how long immunity to SARS-CoV-2 lasts, whether from a previous infection or from vaccination. Pfizer recently said it believes immunity from its shot begins to wane between six to 12 months after vaccination. Some countries, including Israel, Canada, and the U.K., are providing or considering booster shots for certain high-risk patient groups. 

Fauci said that the CDC is currently tracking 20 groups of people who have been vaccinated, to better understand whether there is or will be a need for boosters. This includes thousands of health care workers and people from long-term care facilities and nursing homes. 

“We’re anticipating that this will wane and not plummet,” CDC director Dr. Rochelle Walensky said during the hearing. “As we see that waning, that will be our time for action.”

Much of the discussion around boosters during the hearing pitted lawmakers in favor of additional shots against the regulators and scientists, who urged them to be patient while the U.S. waits on clinical data.

“We can’t just boost [Americans] all the time,” testified Dr. Janet Woodcock, the acting commissioner of the Food and Drug Administration. “We need to boost them when it’s appropriate.”

Pfizer and Moderna Inc.
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are both testing booster shots in clinical trials; Pfizer said this month it plans to share data from that study in August, with plans to file for an updated emergency authorization at some point after that. The National Institutes of Health is also running a Phase 1/2 clinical trial testing Moderna’s vaccine as a booster. 

“I don’t like the time frame, frankly, given the fact that this is being done elsewhere,” said Sen. Mitt Romney (R-Utah).



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