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- Giving two doses of Pfizer eight weeks apart may better protect against the Delta variant.
- One study found that the eight-week delay boosted immune responses more than the 21-day wait.
- It’s a trade-off between the need for two doses and optimizing the immune response, the researchers said.
- See more stories on the Insider business page.
Giving the second dose of Pfizer’s two-dose COVID-19 vaccine eight weeks after the first is the “sweet spot” to protect against the rapidly spreading Delta variant, a British research group has said.
A study published Friday, led by the University of Oxford, found that delaying the second dose for up to 10 weeks boosted antibodies and “helper” T cells that support the immune system more than giving it away. at three weeks, as recommended by Pfizer.
Two doses of Pfizer’s vaccine boosted immune responses greater than one dose, regardless of the time between doses, the study authors from the universities of Oxford, Newcastle, Liverpool, Sheffield and Birmingham added. Waiting longer for a second dose presents a trade-off because people are less protected against the coronavirus after a single injection.
An “ideal place” to protect yourself from the coronavirus
Susanna Dunachie, a global research professor at the National Institute for Health Research at the University of Oxford who co-led the study, told a press conference on Thursday that eight weeks between doses of the vaccine from Pfizer “were the sweet spot”.
The study authors warned that “regardless of the dosage regimen, the study found that the levels of antibodies and T cells varied widely from person to person, which may depend on genetics. , underlying health conditions and past exposure to COVID-19 and other viruses. “
The study on protective T cell immunity against COVID-19 in healthcare workers, or PITCH, which has yet to be peer-reviewed by other experts, has used blood samples from 503 health workers who were mostly white (86%) and female (74%), with an average age of 43 years.
Dr Lance Turtle, Senior Clinical Lecturer in Infectious Diseases at the University of Liverpool, also participated in the study. He said eight weeks between doses is a “reasonable compromise,” but added that there are exceptions. People who are immunocompromised, such as those being treated for cancer, should receive a second dose of Pfizer vaccine as soon as possible, he said.
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The UK is delaying the second dose for up to eight weeks so more people can get their first injection and because a longer interval between doses worked better for other vaccines.
There are risks in delaying the second shot
In the United States, the two doses of Pfizer vaccine are given 21 days apart, as recommended by Pfizer. Dr Anthony Fauci, chief medical adviser to President Joe Biden, has previously said delaying second doses could produce a weaker immune response that feeds variants because people are not fully protected until after receiving both doses.
Nadhim Zahawi, UK Vaccine Minister, said in a press release that the study results were “extremely significant” as they help us “better understand the mechanisms behind our immune response to COVID-19 and the importance of ‘get both doses of the vaccine’.
Previous real-world studies in the UK have shown Pfizer’s vaccine to be 88% effective in preventing symptomatic COVID-19 caused by Delta after two doses, but only 33% effective after a single injection. But the optimal time between doses to protect against the variants is not clear. We also do not know if delaying doses affects the duration of protection.
Dr Rebecca Payne, an immunologist at Newcastle University who participated in the study, said the PITCH study provided “reassuring evidence” that both regimens generate robust immune responses against COVID-19 after two doses .
“We now need to conduct more follow-up studies to understand the full clinical significance of our findings,” she said.
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