Two doses of Covaxin are 50% effective against symptomatic COVID-19, according to the first real-world evaluation of the indigenous coronavirus vaccine in India published in The Lancet Infectious Diseases journal.
The results of an interim study recently published in The Lancet showed that two doses of Covaxin, also known as BBV152, had 77.8% effectiveness against symptomatic illnesses and did not present any serious safety concerns.
The latest study evaluated 2,714 hospital workers at the All India Institute of Medical Sciences (AIIMS) in Delhi from April 15 to May 15, who were symptomatic and underwent an RT-PCR test for the detection of COVID-19.
The researchers noted that the Delta variant was the dominant strain in India during the study period, accounting for around 80% of all confirmed cases of COVID-19.
Covaxin, developed by Hyderabad-based Bharat Biotech in collaboration with the National Institute of Virology, Indian Council of Medical Research (NIV-ICMR), Pune, is an inactivated whole virus vaccine given in two doses, at 28 days interval.
In January of this year, Covaxin was approved for emergency use in India for people aged 18 and over. The World Health Organization (WHO) added the vaccine to its list of approved COVID-19 vaccines for emergency use earlier this month.
The latest study was conducted during the second wave of COVID-19 in India and among healthcare workers who were primarily offered Covaxin.
“Our study provides a more complete picture of the performance of BBV152 (Covaxin) in the field and should be viewed in the context of the peak COVID-19 conditions in India, combined with the potential for immune evasion of the Delta variant,” said said Manish Soneja, additional professor of medicine at AIIMS New Delhi.
“Our findings add to the growing body of evidence that rapid vaccine deployment programs remain the most promising avenue for combating the pandemic, while public health policies must continue to include additional protective measures, such as mask wearing and social distancing, “Soneja said in a statement. .
AIIMS New Delhi’s COVID-19 vaccination center has offered Covaxin exclusively from January 16 this year to all of its 23,000 employees.
Researchers evaluated the vaccine’s efficacy against symptomatic SARS-CoV-2 infection confirmed by RT-PCR.
Of the 2,714 employees in the study population, 1,617 people tested positive for SARS-CoV-2, the virus that causes COVID-19, and 1,097 have tested negative.
Positive cases were matched to negative RT-PCR tests (controls).
The odds of vaccination with Covaxin were compared between cases and controls and adjusted for occupational exposure to COVID-19, previous infection with SARS-CoV-2, and dates of infection.
The study found that the effectiveness of the vaccine against symptomatic COVID-19 after two doses of Covaxin with the second dose given 14 days or more before undergoing an RT-PCR test was 50%.
The efficacy of two doses of the vaccine remained stable over the seven-week follow-up period, the researchers said.
The adjusted vaccine efficacy of the first dose, estimated after seven and 21 days, was low, which is consistent with the performance of other preventive agents against the Delta variant, they said.
“The study results confirm previous research indicating that two doses of BBV152 are needed to achieve maximum protection and that all vaccine deployment plans should follow the recommended dosage schedule,” said Parul Kodan, assistant professor of medicine at AIIMS New Delhi.
“More research is needed to better understand how these findings translate into the efficacy of BBV152 against delta and other variants of concern, particularly related to severe COVID-19 infection, hospitalization and death “Kodan said.
The authors acknowledge that the vaccine efficacy of Covaxin estimated in this study is lower than the efficacy reported by the recently published phase 3 trial. They noted that several factors may be responsible for the reduced efficacy of the vaccine in the latest study.
The researchers said this study population only included hospital workers who may have a higher risk of exposure to COVID-19 infection than the general population.
The research was conducted during the peak of India’s second wave of COVID-19 with high test positivity rates for hospital workers and residents of Delhi, they said.
According to the researchers, the prevalence of circulating variants of concern, particularly Delta, may also have contributed to the vaccine’s lower efficacy.
The authors recognize several limitations to their study.
The study does not estimate the vaccine’s effectiveness against hospitalization, serious illness and death, which require further evaluation, they noted.
In addition, the study was not designed to estimate the effectiveness of the vaccine for different time intervals after vaccination or to determine whether the effectiveness of the vaccine changed over time, the researchers added.