New Delhi, Nov 24, : .A two-dose of Covaxin from Hyderabad-based Bharat Biotech provided only 50% protection against the Covid-19 pandemic in India’s second wave.
This was according to the first real world assessment published in The Lancet Infectious Diseases journal. The study included 2,714 hospital workers from New Delhi’s All India Institute of Medical Sciences, (AIIMS), who were symptomatic and had undergone RT-PCR testing for Covid-19.
The dominant strain in India was the Delta variant, accounting for around 80 percent of all confirmed Covid-19 cases.
“Our study provides a better picture of BBV152’s performance in the field and should also be considered in the contexts of Covid-19 surge conditions, in India, combined, with the possible immune evasive power of the Delta variant,” said Dr Manish Soneja (Additional Professor of Medicine at AIIMS, New Delhi).
Covaxin (BBV152), a vero-cell-derived, inactivated whole virion vaccine, is administered in two doses, 28 days apart, using a novel adjuvant.
BBV152 was approved in India for emergency use for 18-year-olds in January 2021.Earlier this month, the World Health Organization added BBV152 as an approved emergency use Covid-19 vaccination.
Bharat Biotech, in collaboration with the Indian Council of Medical Research-National Institute of Virology-NIV, developed Covaxin shot.
In July, the final results of the Phase-III clinical trials were announced.
According to the company the vaccine had an efficacy rate 77.8% against symptomatic Covid-19 and a 93.4 percent against severe symptomatic infections.
Bharat Biotech published a study in The Lancet earlier this month that showed Covaxin was 77% effective against Covid-19 and 65.2 percent against the Delta variant.
AIIMS researchers have now acknowledged that vaccine effectiveness is lower than the efficacy of BBV152 vaccines in a phase-III randomised controlled study.
1,617 of the 2,714 workers in the study population were positive for SARS-CoV-2, while 1,097 were negative.The adjusted vaccine effectiveness against symptomatic Covid-19 was 50% after two doses BBV152 administered 14 days or more before RT-PCR testing.
Researchers believe that BBV152’s lower effectiveness may be due to the higher risk of infection from Covid-19 among hospital employees than in the general population.
“Our study was conducted at a time when the Covid-19 positive rate in Delhi was approximately 35 percent a” the highest level since the outbreak.This is an important aspect to consider when interpreting the vaccine’s impact.
Professor Naveet Wig is the Head of Medicine at AIIMS New Delhi.
Researchers stressed that these findings add to the growing body of evidence that rapid vaccine delivery programmes are the best path to pandemic control.
They also recommended that additional protective measures such as social distancing and mask-wearing be continued.
The authors acknowledge that there are limitations to the study, such as the fact that it does not assess vaccine effectiveness against death, severe illness, and hospitalisation.This needs further evaluation.The study was not designed in order to estimate vaccine effectiveness at different time intervals after vaccination, or to determine whether vaccine effectiveness has changed over time.
“The decline of vaccine effectiveness against SARS CoV-2 infection during a delta driven surge in cases is not surprising or exclusive to inactivated SARS CoV-2 vaccines including BV152,” stated Dr Ramachandran Thiruvengadam and Dr Akshay Binayke from the Translational Health Science and Technology Institute in a related comment.
They were not part of the study.
“The Delta variant is highly transmissible, infective, and virulent, which can cause severe disease.These attributes may have contributed to a lower vaccine effectiveness against symptomatic diseases.
This has been reported in multiple studies around the world as being as low as 56% for other vaccines.They suggested that future studies should focus on the evaluation of protection against moderate-severe Covid-19.”
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