Slaoui: Could be months before we know if COVID-19 transmission possible after vaccination

Operation Warp Speed’s chief scientific adviser, Moncef Slaoui, said Sunday that it could be months before researchers know for certain if transmission of COVID-19 is possible from a person who has received the vaccine.

On CBS’s “Face the Nation,” host Margaret Brennan asked Slaoui when scientists will know if such transmission is possible, a key factor for determining when the U.S. will develop herd immunity to the virus.

“Do you have a date for when you will know whether once you’ve been vaccinated you can still give the virus to others?” asked Brennan.

“No,” Slaoui responded. “Those studies, frankly, are going to be based on observational data into the population. I don’t think we will have data before late in the spring.”

Does #OperationWarpSpeed have a timeline of once you’ve been vaccinated if you can still give #coronavirus to others?

Slaoui tells @margbrennan “no” with no data projected on such a timeline until late Spring pic.twitter.com/0Ibkk4YWl1

— Face The Nation (@FaceTheNation) January 3, 2021

He also addressed reports of delays in vaccination rollouts around the U.S., pointing as Surgeon General Jerome Adams did in a separate interview on Sunday to a figure indicating that 1.5 million Americans have received vaccines within the last 72 hours.

“Our assumption has been that there is a plan in place to immunize,” Slaoui said of state efforts to distribute the vaccine. “We stand by here to help any specific request. We will do the best we can, as we have done over the last eight months, to make these vaccines indeed make it into the arms of people.”

Top federal officials have defended the U.S. rollout of Pfizer’s and Moderna’s COVID-19 vaccines over the past several days amid reports of a significant gap between the number of vaccines distributed to states, which has totaled more than 14 million, and the number of Americans who have actually been vaccinated. Just more than 4 million doses have been administered in the U.S.

“Somewhere there is a lag in how the numbers are computed, but surely it’s a number that is smaller than the 14 million doses that are out there already available for us,” Slaoui said last week. “We agree that that number is lower than what we hoped for.”