Even as Indian government’s panel of experts is reviewing whether to extend the gap between two doses of the AstraZeneca- Oxford vaccine from four weeks to 8-12 weeks, a new study published in British medical journal Lancet says that a 12-week or three-month interval before the second dose provides better protection.
"In exploratory analyses, a single standard dose of ChAdOx1 nCoV-19 had an efficacy of 76 percent against symptomatic COVD-19 in the first 90 days after vaccination, with no significant waning of protection during this period," Lancet study said.
The study pointed out that the vaccine efficacy after the second dose was even higher at 81·3 percent in those with a dosing interval of 12 weeks or more versus 55·1 percent in those with an interval of less than six weeks.
The study is based on the combined data from clinical trials in the UK, Brazil, and South Africa, which together included a total of 17,178 adult participants.
WHO has already recommended an interval of eight to 12 weeks between doses.
In India, AstraZeneca- Oxford vaccine - manufactured and distributed by Serum Institute of India (SII) under brand name Covishield - was approved for restricted emergency use by Drug Controller General of India (DCGI) with a recommendation of the four to six weeks interval between doses. Covishield’s vaccination course consists of two separate doses of 0.5 ml each. It is recommended that individuals who receive the first dose of Covishield should complete the vaccination course with the second one. The Phase 2/3 bridge trial that SII did for Covishield followed the dosing regimen of two full doses with 4 weeks interval.
Please read here to know about SII's Covishield's package insert factsheet.
Why India should consider this evidence
The extension of interval between the two doses, would certainly help in expansion vaccination coverage faster. India so far
India’s COVID-19 vaccination, which started on January 16, has so far inoculated about 1.8 million of healthcare and frontline workers. Around 8,73,940 people have received the second dose or booster. The numbers look impressive, but considering India's population of 1.3 billion, we haven't yet covered even 1 percent. There is still a long way to go. India needs to scale up vaccination efforts, as cases once again started to rise, to protect the vulnerable population of healthcare, frontline workers, elderly and people with comorbidities.
The other advantage is that the longer interval will help in expanding coverage even as supplies are scarce in the short term.
To be sure, it is still not fully understood whether the vaccine will prevent the human-to-human transmission of SARS-CoV-2, but much of the trial data makes it clear that the vaccine can prevent severe COVID-19 infection, and this will reduce deaths. So use of face masks, physical distancing and hand hygiene along COVID-19 vaccination will be the optimal strategy to help contain the pandemic.
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