An eight-week period between the first and second doses of the Pfizer vaccine is the “sweet spot” to produce a robust immune response against COVID-19, scientists said.
Researchers in the United Kingdom have found that the larger gap between the two doses than the currently recommended three weeks generates higher antibody levels, which offer protection in fighting against infection, the Guardian reported.
“The decision to put it to eight weeks is really balancing all the wider issues, the pros and cons – two doses is better than one overall,” the study’s lead, University of Oxford professor Susanna Duanchie, told the outlet.
“I think that eight weeks is about the sweet spot for me, because people do want to get the two vaccine [doses] and there is a lot of Delta out there right now,” she added, referring to the highly contagious variant.
Pfizer didn’t immediately respond to a request for comment. But the company had warned earlier this year against spacing out doses, saying there was “no data” to support the move.
The UK study, which was commissioned by the Department of Health and Social Care, came after England made the decision to stagger the second dose to 12 weeks after the first when vaccines were in short supply.
Scientists looked at the immune response of more than 500 health care workers who received their doses of the vaccine at different intervals.
The research found that waiting 10 weeks instead of three generated more neutralizing antibodies, which work to stamp out the virus.
“Following two vaccine doses, neutralizing antibody levels were twice as high after the longer dosing interval compared with the shorter dosing interval,” researchers said.
The 10-week gap between doses was still effective against the Delta variant and all other strains of concern, researchers said.
It also improved the response of helper T cells, which support immune memory and aid in reproducing antibodies upon encountering the virus, researchers said.
But scientists said they believe that an eight-week gap is ideal in weighing both wanting patients to experience a strong immune response and trying to have as many people fully protected as possible amid the spread of the virus.
“I can’t see this virus disappearing, so you want to balance that against getting the best protection that you can,” Duanchie told the newspaper.
Nadhim Zahawi, the country’s vaccine minister, said the research reaffirms they made the correct decision in delaying doses.
“This latest study provides further evidence that this interval results in a strong immune response and supports our decision,” Zahawi said in a statement to Bloomberg News.