Generation of efficacy data on 60 years and older population using SARS-CoV-2 vaccines

As of March 31, 2021 nine vaccines against coronavirus-2019 disease (COVID-19 flu) were approved globally, which include ChAdOx1 (AZS1222) (AstraZeneca/Oxford, UK), COVAXIN (Bharat Biotech, India), BNT162b2 (Pfizer-BioNTech, USA), mRNA-1273 (Moderna, USA), ADENO 26 CoV2.S (Johnson &Johnson, USA), Sputnik V (Gamaleya Research Institute of Epidemiology and Microbiology, Moscow, Russia), CORONA VAC (Sinovac Biotech, China), BBIBP-Cor V (Sinopharm, China), and ZF2001 (Anhui Zhifei Longcom, China and Institute of Microbiology, China). All are two-dose vaccines except two, namely ADENO 26 CoV2.S that requires one dose only and ZF2001 that requires three doses. In India, during the same period, only two vaccines namely of AstraZeneca/Oxford by the name COVISHIELD in India, and COVAXIN of Bharat Biotech, Hyderabad were approved. As there is yet no effective therapeutic substance to contain the disease, mass vaccination is the only effective alternative to fight the pandemic. Due to the nonavailability of an adequate supply of ChAdOx1 (AZS1222) vaccine, countries using this one are resorting to delaying the use of the second dose, which must be deployed before the antibody titer is waned off after the first dose. There is a need to experimentally determine how much delay can be made between the two doses for other vaccines also. It was found later that AstraZeneca/Oxford vaccine provided protection after the first dose, up to 90 days, and therefore, the second dose was adopted to be used after 12 weeks. As people over 60 years are more vulnerable to the disease, data need to be generated for each vaccine on this population on whether there is any need to reschedule the dosage gaps as also if new three-dose regimens are more efficacious