12-Week Gap Between Pfizer Vaccine Doses Leads to Higher Antibody Responses

A UK study has shown that individuals over 80 years old had significantly higher antibody responses when given their second Pfizer/BioNTech vaccine dose after 12 weeks as opposed to the standard three-week interval.

The research led by the University of Birmingham analyzed the blood samples of 175 patients after their first shot and again after the second. Ninety-nine patients were given their second jab at the normal three-week mark while 73 were given the dose 12 weeks later.

The elderly patients given their second shot at 12 weeks showed a 3.5-fold increase in their peak SARS-CoV-2 antibody response compared to those in the three-week group, the study found. T- cell immune responses were lower in patients that received the delayed second shot but were comparable to the normal regimen.

“This is the first time antibody and cellular responses have been studied when the second vaccine is given after an extended interval. Our study demonstrates that peak antibody responses after the second Pfizer vaccine are markedly enhanced in older people when this is delayed to 12 weeks,” said the study’s lead author Helen Parry. “This research is crucial, particularly in older people, as immune responses to vaccination deteriorate with age.”

Despite health experts cautioning against long delays between vaccine shots earlier in the pandemic, the UK had moved to adopt the 12-week dosing interval for its Pfizer/BioNTech vaccination program in an effort to ramp up initial inoculations.

Peter English, immediate past chair of the British Medical Association’s Public Health Medicine Committee and a retired communicable disease control consultant, said the study strongly supports that policy, but he found the findings of stronger cellular immune responses in the three-week interval group “puzzling.”

“When we realized, from the phase 3 trials, how effective a single dose was going to be, it meant we could extend the interval, thereby allowing more people to get the protection from a single dose more quickly. Many vaccinologists also predicted that it would enhance the quality of the immune response,” he said. “This paper goes some way to showing just that.” — James Miessler