On March 1 morning, Indian Prime Minister Narendra Modi received his first dose of Covaxin, a COVID-19 jab developed by Indian vaccine maker Bharat Biotech. His taking of the shot represents a major vote of confidence in a COVID-19 vaccine that scientists have widely criticized as unproved.

After getting the vaccine, Modi publicly urged "all those who are eligible" to sign up for jabs, which as of Monday includes Indians over age 60 and those over 45 with qualifying preexisting health conditions.

After launching one of the world's largest vaccination campaigns six weeks ago with health care and frontline workers, India has administered more jabs than all but four countries, but it remains far behind its goal of inoculating 300 million Indian citizens by August. Glitches in India's vaccine app, as well as reluctance to get vaccinated with Bharat Biotech's product, have slowed the rollout.

Like vaccines from Chinese makers Sinovac and Sinopharm, Covaxin uses an inactivated, or killed-off, form of COVID-19 to induce an immune response. Bharat Biotech launched Phase I and II trials for Covaxin in June, followed by a Phase III trial in November with nearly 26,000 volunteers.

But before the Phase III efficacy trials concluded, Indian regulators on Jan. 3 approved Bharat Biotech’s application to distribute the vaccine on an emergency basis in India. At the time, scientists raised questions about why Indian regulators had given the vaccine the green light since Bharat Biotech reportedly had not completed Phase III clinical trials and had not disclosed how effective its vaccine was against COVID-19.

Whereas other vaccine makers like Pfizer and Moderna have published efficacy data—their regimens are 95% and 94% effective, respectively, in preventing COVID-19 infections—no such number is available for Bharat Biotech's Covaxin jab yet.

“We are baffled to understand what scientific logic has motivated the top experts…to approve this vaccine,” the All India Drug Action Network, a medical watchdog in India, said in a statement on Jan. 3. “The decision to approve an incompletely studied vaccine will raise more questions than answers…and likely will not restore faith in scientific decision making bodies.”

Took my first dose of the COVID-19 vaccine at AIIMS.

Remarkable how our doctors and scientists have worked in quick time to strengthen the global fight against COVID-19.

I appeal to all those who are eligible to take the vaccine. Together, let us make India COVID-19 free! pic.twitter.com/5z5cvAoMrv

— Narendra Modi (@narendramodi) March 1, 2021

In response, Bharat Biotech chairman Krishna Ella defended the Indian government’s decision, saying in a press conference that the company had carried out "honest clinical trials" and had a strong track record of making safe and effective vaccines. On Jan. 4, Ella also promised that Bharat Biotech would publish efficacy data on the vaccine within a week.

Nearly two months later, Bharat Biotech has still not publicly established that Covaxin is effective against COVID-19 even as the vaccine has been rolled out across India.

According to Bloomberg's vaccine tracker, India has administered 14.3 million vaccine doses so far, but it is unclear how many of the doses are Covaxin jabs. India's government has also approved another COVID-19 vaccine called Covishield, a vaccine that was originally developed by AstraZeneca and Oxford University but produced by the Serum Institute of India. In the wake of launching India's vaccination campaign on Jan. 16, India's government said it procured 5.5 million Covaxin doses and 11 million Covishield doses.

Bharat Biotech has pledged to release Covaxin data soon.

On Feb. 22, Ella said that his firm would publish Covaxin efficacy data within two weeks and attributed the delay to the structure of Bharat Biotech's trials.

"We moved so fast, but unfortunately we missed the efficacy time point," Ella said. "Had we done the phase 2/3 [trials] combined, we would have captured efficacy faster."

Bharat Biotech's lack of data, however, is creating problems in its rollout.

In February, the central Indian state of Chhattisgarh said that it would stop administering Covaxin until Bharat Biotech could prove the vaccine was effective.

Internationally, Bharat Biotech is reportedly in the process of filing for approval of Covaxin in over 40 countries, but so far Iran is the lone foreign country to authorize the company's application for emergency approval.

Brazil also reportedly purchased 20 million Covaxin doses last week, but some government officials are seeking to block the shipment because of Bharat Biotech's lack of efficacy data.

Now, even as Bharat Biotech's vaccine remains unproved, Modi's vaccine jab signals that the company at least has the support of India's most powerful man.