What is the reason for increasing Covishield second dosage?

India has made two homegrown vaccines for pandemic virus. Covishield vaccine was developed by Oxford University and AstraZeneca and produced in Pune's Serum Institute and Covaxin was developed by Bharat Biotech in Hyderabad. 

Comparison is inevitable for two vaccines on efficacy and second dosage period. Some medical experts have openly said that Covaxin is much better than Covishield. This creates unnecessary doubts and suspicions among the people.

The gap between the two doses of Covishield can be further extended to 12 to 16 weeks. The Healthy Ministry has accepted the recommendation of the Covid Working Group to increase the time frame between two doses of Covishield. Time for the second dose of covishield has changed thrice since January. There is no change suggested for Covaxin which remains at 4-6 weeks. As per the study conducted by Lancet journal, efficacy increased to 81.3% if doses are administered 12 weeks gap. Here people have reasonable doubts. What about the efficacy for the people who completed two doses of Covishield within earlier prescribed 8 weeks?

Opposition parties suspected that timeframe increased not because of science but lack of production in making Covishield vaccine. They blamed that there is no transparency in government decisions. New timeframe will ease the pressure on vaccination centers and the second dose of vaccination will be completed quickly. Once the rush for the second dose is reduced, vaccination for the first dose will complete in a smooth manner. Not only India, there are many nations in the world applying long dosage intervals. UK, Spain, Canada and Bangladesh also maintained 16 weeks gap for second dose of AstraZeneca.