With some Congress leaders raising concerns over the grant of approval to Bharat Biotech's Covid-19 vaccine, Health Minister Harsh Vardhan asserted on Sunday that Covaxin is more likely to work against newer variants of the virus, including the UK variant, and asked politicians not to "discredit well laid out science-backed protocols" followed for approving the jab.
Some Congress leaders, including Anand Sharma, Shashi Tharoor and Jairam Ramesh, on Sunday raised serious concerns over the grant of approval to Covaxin for restricted use, saying it is "premature" and can prove dangerous.
Responding to them, Vardhan said it is "disgraceful for anyone to politicise such a critical issue."
Tagging Tharoor, Ramesh and Samajwadi Party leader Akhilesh Yadav, the health minister said in a tweet, "...don't try to discredit well laid out science-backed protocols followed for approving #COVID19vaccines. Wake up & realise you are only discrediting yourselves!"
Vardhan said, "COVAXIN is more likely to work against newer variants like N501Y Variant (UK variant) & any other that may arise due to antigenic drift as it contains immunogens (epitopes) from other genes in addition to those from Spike protein."
SP president Yadav said the Covid-19 vaccination programme is a "sensitive process" and the government should not treat it as a "cosmetic" event as it is a matter of lives.
Covaxin has been indigenously developed by Bharat Biotech in collaboration with the Indian Council of Medical Research (ICMR).
ICMR Director General Balram Bhargava also said Covaxin is based on an inactivated whole virus, having potential to target mutated coronavirus strains including the UK variant, which was a major ground for giving it a conditional nod.
He, however, said no clear data regarding the efficacy of the vaccine is available so far.
The data generated so far demonstrates a strong immune response (both antibody as well as T cell) and in-vitro viral neutralisation. The ongoing clinical trial is the largest trial on 25,800 subjects, in which already 23,000 volunteers have been enrolled including subjects with comorbid conditions, and the vaccine has demonstrated safety till date, Bhargava said.
Further allaying apprehensions surrounding the Bharat Biotech vaccine, Vardhan said there were no seroconversions in those who were provided vaccines in Phase II as well as Phase I of Covaxin clinical trials.
Seroconversion is the transition from the point of viral infection to when antibodies of the virus become present in the blood.
"Our experience with inactivated vaccines not having serious adverse events was also observed in Phase II done among 380 study participants in BBV152 trial in 21280 Person days follow up. No serious adverse events seen. Only 7 per cent persons receiving 6 microgram dose had mild symptoms," Vardhan said in another tweet.
"The data from COVAXIN Phase I & II clinical trials reveals that it not only produces neutralizing antibodies in all participants but also sensitises CD4 T lymphocytes that imparts durable immune response," Vardhan tweeted.
He said vaccines approved globally based on gene encoding spike proteins have protective efficacy of over 90 per cent.
"However, COVAXIN based on whole inactivated virus has other antigenic epitopes in addition to spike protein. So,it's likely to have similar protective efficacy reported for others," he said.
India's drugs regulator on Sunday approved Oxford Covid-19 vaccine Covishield, manufactured by the Serum Institute, and indigenously developed Covaxin of Bharat Biotech for restricted emergency use in the country, paving the way for a massive inoculation drive.
The Drugs Controller General of India (DCGI) granted approval on the basis of recommendations by a Covid-19 Subject Expert Committee (SEC) of the Central Drugs Standard Control Organisation (CDSCO).
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