Dr. Anthony S. Fauci, the nation’s leading infectious disease expert, told CNN on Friday that the United States would not follow Britain’s lead in loading the first vaccine injections, potentially delaying the second dose.
The UK this week announced a plan to delay the second intake of its two licensed vaccines developed by Pfizer and AstraZeneca to allow more people the partial protection afforded by a single dose.
“I wouldn’t be for it,” said Dr. Fauci told CNN’s Elizabeth Cohen. “We’ll keep doing what we’re doing.”
His opinion was endorsed by a number of experts, including Dr. Eric Topol, clinical trial expert at the Scripps Research Translational Institute in California, tweeted, “This is good because it follows known study data with an exceptional 95 percent effectiveness, avoidance of extrapolation and the unknown. “
While clinical trials tested effectiveness two or four weeks after the first second dose given, British officials said they would allow a gap of up to 12 weeks. Such delays have not been rigorously tested in trials. For example, the Pfizer BioNTech vaccine has been shown to be 95 percent effective at preventing Covid-19 when given in two doses three weeks apart.
Deviating from this regime “is like going to the Wild West,” said Dr. Phyllis Tien, an infectious disease doctor at the University of California at San Francisco. “It has to be data-driven if you want to change something.”
Widening the gap between vaccine doses could weaken the benefits of the second shot, which is said to boost the body’s defenses against the coronavirus and increase the strength and durability of the immune response. In the meantime, the protective effects of the first shot could wear off faster than expected.
“We don’t really know what happens if you only have one dose after about a month,” said Natalie Dean, biostatistician at the University of Florida. “It’s just not how it was tested.”