Bharat Biotech, the manufacturer of coronavirus vaccine Covaxin, on Wednesday criticised a recent study that found that its jab produced significantly fewer antibodies than Covishield.

In a statement, the Hyderabad-based company claimed that the study “had lots of flaws”, ANI reported.

The company also said that the phase 3 trial data for Covaxin will be made public in July. The indigenously developed vaccine was granted an emergency use authorisation in January – despite there being no phase 3 trial data. The company had then said it would submit efficacy results by March.

“It is not a peer-reviewed publication, nor statistically and scientifically designed study, the study design and conduct reflect an ad hoc analysis, rather than predetermined hypothesis,” Bharat Biotech said while trashing the findings.

The company said that the study was not registered on the government’s Clinical Trial Registry and not approved by the Central Drugs Standard Control Organisation.

Before this formal response, Raches Ella, head of business development and advocacy at Bharat Biotech, had taken to Twitter to express displeasure about the study. In a series of tweets, Ella said he was “surprised that media/researchers are concluding based on non-peer-reviewed work”.

One of the researchers involved in the study, AK Singh, responded sharply to Ella’s tweets. He pointed out that Bharat Biotech was yet to furnish results of its phase 3 trials, nearly half a year after it was issued emergency authorisation.

“Brother, whole country is getting vaccinated even without a preprint phase 3 results – lest forget published one,” he wrote. “We owe a sincere gratitude to Bharat Biotech but that doesn’t mean one should raise finger on others effort. Of course we will produce published results finally.”

The study that Bharat Biotech has raised objections to is a pre-print that concluded based on observational data that while both vaccines elicited good immune response after two doses, the amount of antibodies that was detected in recipients of Covishield was much higher than those who got Covaxin.

The study, first reported on June 6, showed that one dose of Covishield produced 10 times more antibodies than Covaxin. After a second dose was added, it was found that two shots of Covishield produced about six times more antibodies than Covaxin.

The study is yet to be peer reviewed but was shared on medRxiv, an online portal for unpublished reports on medical sciences. This is the first study of its kind – that compares Covaxin and Covishield. However, many other scientists have pointed out what they claimed to be serious flaws in the study’s design.

In its statement against the study, Bharat Biotech added that the phase 3 trial data will first be be submitted to the Central Drugs Standard Control Organisation, followed by peer-reviewed journals.

“Once data from final analysis of phase 3 studies are available, Bharat Biotech will apply for full licensure for Covaxin,” the company said.