Why the interval between first and second Covishield doses must now be shortened

Why the interval between first and second Covishield doses must now be shortened How did the dosing interval get longer?Two studies were cited mainly for increasing the interval. In a Lancet study published earlier this year, efficacy result in phase-3 clinical trial of two doses of Oxford-AstraZeneca (Covishield equivalent) was 55. https://ift.tt/eA8V8J