Pfizer’s dose gap is longer Coronavirus disease A British study on Friday found that the overall antibody level caused by the vaccine was higher than the short gap, but the antibody level dropped sharply after the first dose.
The research may help inform vaccination strategies for Delta variants, which will reduce the effectiveness of the first dose of COVID-19 vaccine, even if two doses of the vaccine are still protective.
“For longer dosing intervals… after a single dosing, the neutralizing antibody level against the Delta variant is not well induced and cannot be maintained during the interval before the second dosing,” The author of the study, which was led by Oxford University, said.
“After two vaccinations, compared with the shorter dosing interval, the neutralizing antibody level is twice as high after the longer dosing interval.”
Neutralizing antibodies are believed to play an important role in immunity to coronaviruses, but not all of them. T cells also play a role.
The study found that compared with the short-dose regimen of 3-4 weeks, the overall T cell levels in long gaps are 1.6 times lower, but a higher proportion are “helper” T cells with long gaps, which support long-term immune memory.
The author emphasized that in a study of 503 medical staff, any of the dosage regimens produced strong antibody and T cell responses.
The results of the study published as a preprint support the view that although a second dose is required to provide full protection against Delta, delaying that dose may provide longer-lasting immunity, even if this is at the cost of short-term protection.
In December last year, the United Kingdom extended the vaccination interval to 12 weeks, but Pfizer warned that there is no evidence to support getting rid of the three-week interval.
The UK now recommends an 8-week interval between vaccine doses in order to provide more people with high protection against Delta faster, while still maximizing the immune response in the long term.
“I think week 8 is the best time point,” Susanna Dunachie, co-lead researcher of the study, told reporters.
(Reporting by Alistair Smout; Editing by Giles Elgood)
