Covaxin interim data shows it is 77.8% effective against symptomatic Covid, gives 65.2% protection from Delta variant: The Lancet

Bharat Biotech’s Covaxin demonstrates 77.8 per cent efficacy against symptomatic Covid-19, peer-reviewed general medical journal The Lancet confirmed. As per phase-three clinical trials data, Covaxin is also the only Covid-19 vaccine that has demonstrated efficacy data against delta variant at 65.2 per cent and 70.8 per cent protection against all variants of SARS-CoV-2 variants, a statement by Bharat Biotech said. Covaxin will be 93.4 per cent effective against severe symptomatic Covid-19 patients, the data further said.

The efficacy data comes a few days after the World Health Organization gave a green signal to Covaxin for use among people aged 18 years and above and the United States, the United Kingdom put it in the approved list of vaccines for foreign travelers.

Dr Balram Bhargava, Director General of ICMR sees the publishing of efficacy data of Covaxin in The Lancet speaks about its strong position amongst other global Covid-19 vaccine front-runners.

Dr Krishna Ella, Chairman and Managing director of Bharat Biotech informed that Covaxin has been mentioned in more than 10 peer-reviewed journals making it one of the most highly-published Covid-19 vaccines in the world.

Covaxin is an inactivated vaccine developed using Whole-Virion Inactivated Vero Cell-derived platform technology. “They contain dead virus, incapable of infecting people but still able to instruct the immune system to mount a defensive reaction against an infection,” said Bharat Biotech’s website. The vaccine is administered in a two-dose regime in a period of 28 days.
Covaxin efficacy trial & findings

The Bharat Biotech International Limited and the Indian Council of Medical Research (ICMR) funded study was conducted between November 16, 2020, and May 17, 2021, and included a total of 25,798 subjects of which 14,419 are adults who were administered two doses of the vaccine and 12, 198 who got placebo at 25 hospitals across the country.

The efficacy data were then prepared based on 1130 symptomatic Covid cases among 16,973 participants who were initially seronegative and subjected to a test at least two weeks after participants had received a second dose.

Out of a vaccinated group of 8,471 people, 24 were positive cases while in the placebo group of 8,502, 106 contracted the infection. 1 participant among the positive cases in the vaccinated group and 15 in the placebo group was severely symptomatic. This data suggested overall efficacy of 77.8 per cent.

No severe vaccine-related adverse effect was noticed among the participants and a few adverse effects reported like headache, fatigue, fever was mild and occurred within seven days of vaccination. Moreover, the adverse effects were similar to placebo with 12 per cent of subjects experiencing common side effects, the statement said.

Covishield and its efficacy

Another widely administered Covid-19 vaccine Serum Institute of India’ Covishield, a version of the Oxford-AstraZeneca vaccine, or ChAdOx1 nCoV-19 peer-reviewed efficacy rate published in The Lancet in December 2020 and later updated in March 2021 shows the efficacy of 81.3 per cent against symptomatic Covid on administering complete vaccination regime in a 12-week period.

Limitations of the efficacy study

They noted, however, that this data should be presented as preliminary and further observations are necessary to confirm clinical efficacy against Delta and other variants.

Apart from calling the data preliminary, the researchers noted that they could not calculate efficacy after a single dose due to the low number of cases reported in between two doses in 28 days and a larger sample size is needed for the same.

Also, all the participants here were from India and therefore lacked ethnic and racial diversity. hence the efficacy of the vaccine in the global population cannot be determined.