How effective and beneficial is it to have a longer wait period between COVID doses?

Would the Indian COVID-19 task force be able to give people one final, definite gap between the two vaccine doses before everybody gets vaccinated? Neither is the question rhetorical, nor the tone sarcastic. It is a matter of fact. At present, the gap is 12 to 16 weeks between doses. It was an increase from six to eight weeks, announced in May. The original gap was four to six weeks. The National Technical Advisory Group on Immunisation (NTAGI) was embroiled in a controversy over the gap issue. It was said they were merely following the UK example. It was also said there was no unanimity among the advisory group members when the latest gap extension was announced. The Government denied everything and, in its very latest statement, said that there is no need to change the existing interval between doses. In the same breath, however, NITI Aayog member VK Paul insisted there is a “window of opportunity to make further changes, but not now”. And we now have yet another British study, this time from the University of Oxford, which says a longer gap of around 10 months — between 40 and 45 weeks — improves the immune responses to the AstraZeneca COVID-19 vaccine. The research paper, published this Monday, is yet to be peer-reviewed. The full details of the study are awaited to see if the objective was to find out the best interval for maximum levels of antibodies in vaccine volunteers or optimum efficacy of the vaccine to resist the infection.

How the longer gap would impact the COVID-19 variants, like Delta Plus, is also yet to be known. The Oxford paper said something interesting altogether and is worth quoting: “A single dose of ChAdOx1nCov-19, with a second dose given after a prolonged period, may, therefore, be an effective strategy when vaccine supplies are scarce in the short term. A third dose results in a further increase in immune responses, including greater neutralisation of variant SARS-CoV-2 viruses, and could be used to increase vaccine efficacy against variants in vulnerable populations.” The question is whether the interval between doses is stuck between science and logistics; whether it is determined by a scientific process to improve antibodies or by the logistical matter of availability of vaccine? Second, the study is already talking about a third dose — after an as-yet unspecified gap — to boost immunity in “vulnerable populations”. Is it the case that there can be a vulnerable population even after being fully vaccinated or is it that the entire population will need a third, booster dose? What the scientists of the Indian task force should determine is if it is at all possible to redesign the vaccines instead of continuing with studies to find the elusive, ideal gap between doses. There is a need for the Government to assuage the people that irrespective of the frequently changing intervals, the basic immunity and efficacy levels for all gaps would not be compromised.