A gap of eight weeks between the first and second doses of Pfizer’s and BioNTech’s COVID-19 vaccine is the “sweet spot” for dosing, a UK research team said.

Although the authorized dose interval for the vaccine is three weeks, a study commissioned by the UK’s Department of Health and Social Care found that a 10-week interval between doses produced more antibodies and T-cells against infection.

However, given concerns about the rapidly spreading Delta variant, an 8-week window was deemed preferable by the researchers from Oxford and Newcastle universities.

In May, a UK Joint Committee on Vaccination and Immunization expert panel recommended an eight-week dosing interval, revising an earlier call for a 12-week dosing interval.