Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he continued to believe it better to inject Americans with two doses of the Pfizer and Moderna vaccines on the drugmakers’ recommended schedule — a view that is at odds with other Biden administration advisers.

Some experts, like Michael Osterholm, an epidemiologist and former adviser to President Joe Biden, have called for delaying the second dose of the vaccine until more of the initial doses are administered. The British government has delayed second doses, enabling it to reach more of its population more quickly with a single dose, and its death rate from COVID-19 has declined more quickly than that of the United States.

Fauci, speaking during a White House COVID-19 task force briefing on Monday, acknowledged that there are different approaches and opinions related to vaccine distribution.

But he argued that data that showed that a single dose of the Pfizer or Moderna vaccine is 80 percent effective in preventing infection, often cited by those who prefer the British approach, is tenuous because the level of neutralizing antibodies against the virus may not last as long.

“When you’re dealing with variants that clearly might actually be diminished somewhat in their capability of the vaccine-induced antibodies to essentially be able to neutralize them, you are in a tenuous zone if you don’t have the full impact,” Fauci said.

He acknowledged that there is some merit to the case for delaying second doses but said that the federal government would continue to advise taking both shots on schedule. Pfizer recommends its vaccine doses be spaced three weeks apart, while Moderna advises a month between injections of its vaccine. With that spacing, both vaccines are 90 percent effective at preventing COVID-19 two weeks after the second shot, according to the Centers for Disease Control and Prevention.

“Right now, given the number of vaccines we are able to give every day, literally every day that goes by we get closer and closer to where we want to be. For that reason, although we always continue to keep an open mind, we consider the route that we’re on now as the best route,” said Fauci.

Meanwhile, both Fauci and Andy Slavitt, a White House senior adviser on COVID-19, sought to reassure the public that the Johnson & Johnson vaccine, which requires only one dose, is safe after a manufacturing error by a subcontractor ruined 15 million doses.

“All of the Johnson & Johnson vaccines that have been available in the U.S. have been authorized by the FDA. None of it came out of this plant in question,” Slavitt said. 

The seven day COVID-19 case average for the U.S. is currently 3.1 million shots per day, and the task force announced that on Saturday the U.S. reached a new high of 4 million shots administered in a 24-hour period.

In addition, as of Monday nearly one-third of all Americans and 40 percent of those age 16 or older — since the FDA has not authorized any vaccine for children younger than that — have received at least one shot, with one-quarter of them now fully vaccinated. Three quarters of seniors have had at least one dose of a vaccine, and 55 percent are fully vaccinated.

Still, CDC Director Rochelle Walensky warned that confirmed COVID-19 cases have also increased for four straight weeks.

The seven-day average of cases has increased to 64,000 per day, which is up 7 percent from the prior seven day period. Hospital admissions also climbed 3 percent to 4,970 per day from the previous period. COVID-19 deaths continue to decline and are now averaging 800 per day.

The CDC stressed the importance of adhering to its safety guidelines, especially for schools.

“As we have been working with states and understanding their individual outbreaks among younger people, I want to sort of underscore that this is among 18 to 24 year olds where we are seeing actually peaks in case,” Walensky said, adding that many of the cases are related to extracurricular activities and youth sports.