India, UK studies at odds on single-dose Covid-19 vaccine benefits

N K Arora has said the Covid Working Group would ignore the UK study’s findings given its small sample size

The next leg of India’s Covid-19 vaccination drive could be shaped by how effective a single dose of the vaccine is in protecting against the deadly virus. Faced with the uphill task of inoculating a massive population and ambitious targets to meet by the end of the year, the government has hinted that it could switch to a single-dose regime if the benefits of twin doses prove lackluster.

The adoption of a single-dose policy would effectively render the debate around vaccine intervals meaningless, which itself has been a thorn in the government’s side. However, with new and more dangerous variants thrown into the mix, any decisions could have severe ramifications for a potential third wave.

Indian studies show meagre benefit

Recent studies conducted in India have shown little to choose between the protection offered by either policy. N K Arora, chairperson of the Covid Working Group that advises the government on vaccine policy, has highlighted the results from two such studies, while dismissing contradictory findings from studies conducted in the United Kingdom.

Last week, a preprint paper by researchers at Vellore’s Christian Medical College (CMC) that mainly involved the Covishield vaccine found a single dose of the vaccine offered 61 per cent protection from the Delta variant, which grew only slightly to 65 per cent after a second dose.

Also Read | Single Covishield dose 61% effective against Delta variant: Covid-19 panel head

Arora also referred to a study carried out by PGI Chandigarh that clocked vaccine effectiveness at 75 per cent for both partially immunised and fully immunised participants, though he mentioned that the study was focused on the Alpha variant and not the more virulent Delta variant.

"In the short run, the protection from serious disease, hospitalisation, and death is similar whether one has received one dose or two doses of Covishield and Covaxin," Arora said.

UK studies push for two

A real-world study in the United Kingdom, conducted by Public Health England, claimed that a single dose of the Oxford-AstraZeneca vaccine — Covishield in India — gave the recipient 33 per cent protection against the Delta variant and about 50 per cent protection against the Alpha variant. After two doses, protective cover improved to 60 per cent against the Delta variant and 66 per cent against the Alpha variant.

The gap of 30-40 percentage points between the Indian studies and the UK study when it comes to the first dose is statistically significant and could potentially sway vaccine policy towards a single-dose regime. Moreover, Arora has told The Wire that India would ignore the UK data because of its relatively small sample size, which was an eighth of that in the CMC study.

The question of dosage and gaps now depends on whether policymakers prioritise full coverage over wider coverage. While India has administered the largest number of first doses in absolute terms, as a percentage of its population, the inoculation drive has been sluggish. To add to that, the country is the worst performer in terms of fully vaccinating its citizens as under 4 per cent of the population has received both jabs so far.