Covaxin dosage 50% effective against symptomatic covid: the real world
Results of an interim study published in The Lancet Infectious Disease journal showed that two doses of the vaccine manufactured by Bharat Biotech Covaxin, also known as BBV 152, had 77.8 percent efficacy against symptomatic disease and no serious safety concerns. .
The study titled ‘Efficacy of an inactivated virus-based SARS-CoV-2 vaccine, BBV152 in India: a trial-negative, case-control study’ evaluated 2714 hospital workers at the All India Institute of Medical Sciences (AIIMS) in Delhi. , from April 15 to May 15, who were symptomatic and underwent RT-PCR test to detect COVID-19.
The researchers, including doctors Manish Soneja, Adil Rashid Khan, Debashish Desai, Ankit Mittal and others, said they did not receive any funding for the study and the protocol for it was approved by the AIIMS ethics committee.
The researchers also noted that the delta variant was the dominant strain in India during the study period. At the time, the delta variant accounted for nearly 80 percent of all confirmed Covid19 cases.
Of the 2,714 employees in the study population, 1,617 people tested positive for SARS-CoV-2 infection, the virus that causes COVID-19, and 1,097 tested negative.
The researchers evaluated the vaccine’s effectiveness against symptomatic RT-PCR confirmed SARS-CoV-2 infection. The study found that the vaccine effectiveness against symptomatic COVID-19 was 50 per cent after two doses of Covaxin with a second dose 14 or more days before the RT-PCR test. The researchers also noted that the effectiveness remained stable over the seven-week follow-up period.
“The vaccine efficacy estimated in our study is less than the efficacy declared after the completion of Phase 3 trial, despite a similar testing strategy being used (COVID-19 determined through SARS-CoV-2 RT-PCR test). test for participants with symptoms of (weekly telephone follow-up),” the researchers noted in the study.
He argued that several factors could be responsible for the observed low effectiveness in this study.
“First, the population included in our study included only hospital workers who were exposed to a higher risk of SARS-CoV-2 infection than the general population,” it said. He said the research was conducted during the peak of the second wave of COVID-19 in India, which had high test positivity rates for both hospital staff and residents of Delhi. “As on April 26, 2021, the test-positivity rate for Delhi was around 35%, the highest since the start of the pandemic,” noted the researchers.
“Thus, our results can only reflect the performance of BBV152 under such growth conditions,” he said.
The prevalence of circulating forms of anxiety, particularly the delta variant, may have contributed to the reduced effectiveness of BBV152.
“Although in-vitro studies have shown these variants to be neutralized by both convalescent and post-vaccine sera, the neutralization titers are several times lower than those of the variants, especially the delta variant,” the study said.
The Phase 3 trial of BBV152 was conducted during a period when the overall test-positivity rate was low, and the prevalence of the delta variant among positive cases was largely unknown.
“In contrast, at the end of April, 2021, the period during which this study was conducted, the delta variant was the dominant strain, accounting for over 80% of all sequenced genomes as reported by Indian SARS-CoV. 2 Genome Sequencing Consortia,” noted the authors.
The researchers acknowledged several limitations to their study. He said it does not predict the vaccine’s effectiveness against hospitalization, serious illness and death, which requires further evaluation. The study was not designed to estimate vaccine effectiveness for different time intervals after vaccination or to determine whether vaccine effectiveness changed over time, he said.
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