Of the vaccines against COVID-19 approved in India, Covovax would be a better booster for those who were administered Covishield jabs than another dose of the same vaccine, according to the data available presently, noted virologist Dr Shahid Jameel said.

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Jameel, the former head of the advisory group to the Indian SARS-COV-2 Genomics Consortia (INSACOG), said there is no data for the other combinations of vaccines as of now. "Data available at this time suggests that of the vaccines approved in India, Covovax would be a better booster in Covishield-vaccinated people than another dose of Covishield," he stated.

Officials have, however, said the "precaution dose" will be a third dose of the same vaccine that a person has taken. Covovax has been developed by US-based vaccine maker Novavax Inc. that had announced a licence agreement with the Serum Institute of India (SII) for the development and commercialisation of NVX-CoV2373, its COVID-19 vaccine candidate, in low and middle-income countries and in India.

The central drug authority, CDSCO, approved Covovax on 27 December. India is gearing up to tackle a possible third wave of the coronavirus pandemic as the Omicron variant of the virus, which is said to be much more infectious than the other strains of COVID-19, has surfaced.

The country has recorded 781 Omicron cases across 21 states and Union territories so far. Of the patients, 241 have either recovered or migrated, according to the Union health ministry. In an interview to news portal 'The Wire', noted virologist Gagandeep Kang said there is presently no data in India regarding which vaccine should be used for the third dose.

However, she cited a UK study that gauged the immune response generated in individuals who have already received two doses of the AstraZeneca (Covishield) vaccine by either a booster dose of the same vaccine or one of the Novavax (known in India as Covovax) vaccine.

The study found that a third dose of Covishield increased the Geometric Mean Ratio (GMR) by 3.25, while a booster dose of Covovax increased the same by eight times and one of an mRNA vaccine did so by 24 times, she said.