Public health experts suggest that India could consider delaying the second dose of the COVID-19 vaccine to improve immunogenicity. The second dose is currently given 28 days after the first one. 

Dr Gagandeep Kang, member of the Strategic Advisory Group of Experts (SAGE), said that delaying the second dose was not only about supply constraints, but it also improved efficacy.

A study published in Lancet has shown that the Oxford-AstraZeneca vaccine had greater efficacy when the second dose was given after a gap of 12 weeks, instead of 4. The study included more than 17,000 participants. The efficacy of the vaccine increased from an average of 55.1%, after two doses given less than six weeks apart, to 81.3% when the gap between the doses was at least 12 weeks. Kang stated that findings from the clinical trials with the Oxford-AstraZeneca vaccine suggest that a longer interval between doses improved the immune response as well as vaccine efficacy… (ET Healthworld – TNN, March 12, 2021)