Is One Dose Of Covishield Enough To Fight COVID? What Experts Say
The efficacy of a single dose of Covishield against the B.1.617.2 variant which is prevalent in India was found to be close to 33%.
In an effort to 'fine-tune' vaccination strategy that aims to scale up daily administered doses in India, the Centre plans to test the effect of one dose of Covishield instead of the prescribed two doses on its citizens, government sources told several news organisations. Earlier reports had already suggested that the Centre plans to study a mix-and-match regimen-- mixing different vaccines.
BOOM spoke to three biologists who all agreed that there is not enough data to substantiate implementing a single-dose regimen in the country but differed on their opinions of conducting studies for the same.
Vaccines such as Johnson and Johnson as well as the Sputnik that use the same viral vector technology for vaccine-making as Astrazeneca are single dose. So, the government believes that the Oxford-AstraZeneca vaccine could also be equally effective with only one dose. However, a study carried out in the UK by scientists at Public Health England found that a single dose of Covishield was only 33% effective against the B.1.617.2 variant that is rampant in India. At two doses, the vaccine was doubly effective as it showed 60% efficacy against this variant.
Taking a note of this study, Anurag Agarwal, Director, Council of Scientific and Industrial Research (CSIR)-Institute of Genomics and Integrative Biology, had told The Hindu that health workers, frontline workers and the people in the elderly community will need to receive two doses of the vaccine.
Not Enough Data
BOOM spoke to Dr. Sharvan Sehrawat, immunologist, Indian Institute of Scientific Education and Research (IISER), Mohali to understand the relevance of using a one-shot vaccine in India.
"One dose is going to give some kind of immunity. Even the UK tried to prioritise vaccinating its whole population by giving everyone a single dose first, and it worked. We do not have enough data, but it is quite possible that the same regime might work in India," Sehrawat opined.
Dr. N K Ganguly, former director-general, Indian Council of Medical Research and Dr. Sankaran Krishnaswamy, co-founder of Indian Scientists Response to COVID-19, and retired Professor of Bioinformatics, Madurai Kamraj University agreed that there is not enough data but both believed that following a two-dose regime will produce better outcomes.
Is This Due To Vaccine Shortage?
Dr. Ganguly highlighted that both the Johnson and Johnson viral vector vaccine and the Sputnik Light vector vaccine are single-dose vaccines and as they use similar technology to the Oxford-AstraZeneca vaccine, it is plausible to implement the same rule. However, he said that there is not enough data.
"A single dose has only shown 30-40% efficacy while that increased to 80% after the second dose. The UK followed a single dose regime for a short period as it was facing a shortage of vaccine doses and wanted to vaccinate a larger proportion of its population. Both Sputnik light and Johnson and Johnson have data backing their single-dose usage," explained Dr Ganguly.
The former director-general of ICMR said that unless India has data supporting its move or has a valid reason for it, such as vaccine shortage, the double dose regime should continue.
Dr Krishnaswamy wanted to know if the government is going to register a trial with the Clinical Trials Registry for checking a single-dose efficacy. India has so far only relied on the results carried out in the UK for bringing about changes in the dosage or changing the gap between the duration of the two doses.
"First, they keep changing the duration for taking the vaccines, and now if they are planning this move, it shows that they did not place enough orders of the vaccine in the first place. If you are looking to vaccinate your adult population, the government should have arranged for at least 1.2 times the population. Some countries have even ordered doses 5 times the population," said Dr Krishnaswamy.
Also Read: "Wake Up And Smell The Coffee": Supreme Court To Centre On Vaccine Policy
How Will This Affect Breakthrough Infections?
If a person gets infected after receiving even one dose of the vaccine, it is considered a 'breakthrough infection'. According to government data as of May 18, 23,940 people in India got the infection after taking Covaxin -- 0.13 per cent of the total vaccinated so far. Of these, 18,427 were infected after the first dose, while 5,513 were infected after the second dose.
Similarly, 1,19,172 breakthrough infections have been reported after taking Covishield, which is 0.07 per cent of the administered doses. Of these, 84,198 got infected after the first dose, while 34,874 got infected after the second dose.
Both Sehrawat and Ganguly agreed that breakthrough infections could increase if a single dose vaccine is administered. Sehrawat, however, added that these cases would have milder bouts of COVID-19 as compared to not being vaccinated at all.
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