Dr Anthony S. Fauci, the country’s leading expert on infectious diseases, told CNN on Friday that the United States would not follow Britain’s lead to pre-load the first vaccine injections, which could delay the administration of second doses.
Britain this week announced a plan to postpone the second shots of its two authorized vaccines, developed by Pfizer and AstraZeneca, in an effort to grant the partial protection of a single dose to more people.
“I will not like it,” said Dr. Fauci told Elizabeth Cohen, CNN. “We’re going to keep doing what we do.”
His advice was endorsed by some experts, including Dr. Eric Topol, a clinical trial expert at the Scripps Research Translational Institute in California, who tweeted, “It’s good, because it follows what we know, the test data with extraordinary efficiency of 95 percent, to avoid extrapolation and the unknown.”
While clinical trials tested the efficacy of second doses three to four weeks after the first test, UK officials said they would allow a gap of up to 12 weeks. Such delays have not been carefully tested in trials. The Pfizer-BioNTech vaccine has been shown to be 95 percent effective at preventing Covid-19 when administered in two doses, three weeks apart.
To stray from this regime ‘is like entering the wild west’, said dr. Phyllis Ten, a physician at Infectious Diseases at the University of California, San Francisco, said. “It has to be data-driven if they’re going to make a change.”
Enlarging the gap between the vaccine dosage can strengthen the benefits of the second shot, which is meant to boost the body’s defenses against the coronavirus, which increases the strength and durability of the immune response. In the meantime, the protective effects of the first shot may also diminish faster than expected.
“We do not really know what happens if you only have one dose after about a month,” said Natalie Dean, a biostatistician at the University of Florida. “It just’s not the way it’s been tested.”