While clinical trials tested the efficacy of second doses delivered three or four weeks after the first, British officials said they would allow a gap of up to 12 weeks. Such delays have not been rigorously tested in trials. The Pfizer-BioNTech vaccine, for instance, was shown to be 95 percent effective at preventing Covid-19 when administered as two doses, three weeks apart.
Straying from this regimen “is like going into the Wild West,” said Dr. Phyllis Tien, an infectious disease physician at the University of California, San Francisco. “It needs to be data driven if they’re going to make a change.”
Widening the gap between vaccine doses could risk blunting the benefits of the second shot, which is intended to boost the body’s defenses against the coronavirus, increasing the strength and durability of the immune response. In the interim, the protective effects of the first shot could also wane faster than anticipated.
“We don’t really know what happens when you only have one dose after, like, a month,” said Natalie Dean, a biostatistician at the University of Florida. “It’s just not the way it was tested.”
Source Article from https://www.nytimes.com/2021/01/01/world/dr-fauci-advises-against-the-british-approach-of-delaying-a-second-dose-of-vaccine.html
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