Photo/Illutration Children wait to receive free food distributed in a slum during a lockdown to check the spread of the new coronavirus in Mumbai on April 18. (AP file photo)

NEW DELHI--A plan to give the anti-malarial drug hydroxychloroquine to thousands of people in Mumbai’s crowded slums to prevent coronavirus infections has temporarily been shelved, officials said Wednesday.

Health officials in Mumbai said that a test to prove the efficacy of the much touted but largely untested drug was still in the cards, but that for now they would follow federal Indian guidelines.

India, which reached the grim milestone of over 1,000 deaths from the virus on Wednesday, is one of the few countries that has pushed for the use of hydroxychloroquine, as a precautionary measure among high-risk groups such as health care workers or people who have come in close contact with COVID-19 patients.

Mumbai, one of the world’s most densely populated cities, has struggled to contain the spread of the virus, and has over 3,000 cases. In Mumbai slums like Dharavi, which is Asia’s largest, social distancing is nearly impossible. In response, the state government had said it would conduct a clinical trial to test the effectiveness of hydroxychloroquine on slum residents.

But experts pointed to the scant evidence for the efficacy of the drug and the risks it poses, and questioned the ethics of using hydroxychloroquine on a vulnerable population. Daksha Shah, Mumbai's deputy executive health officer, said that officials would now follow guidelines set by India’s top medical research body, and that they were waiting for approval to test the drug.

The state government has now said that hydroxychloroquine--which has been touted by U.S. President Donald Trump--can be given only after patients consent to taking it while knowing the risks involved. It added that adverse reactions need to be immediately reported to authorities, and that doctors must sign off on giving the drug to those with heart ailments, diabetes or blood disorders.

But concerns remain over India’s policy of using the drug as a precautionary measure. India's National Task Force for COVID-19 issued a statement on March 22 that said its decision to allow the use of the drug was based on “risk-benefit considerations, under exceptional circumstances” and was “derived from available evidence of benefit as treatment and supported by preclinical data.”

After the statement was issued, health workers in Mumbai, like other parts of India, began taking hydroxychloroquine. The drug was also given to healthy police officers in the city.

But experts say there is no evidence that the drug is a preventative tool against COVID-19. Even for the treatment of diagnosed patients, hydroxychloroquine has shown no benefit.

An analysis of 368 patients in U.S. veterans hospitals published earlier this month reported more deaths among those given the drug versus standard care.

“If there is no evidence ... why are scientific bodies pushing this drug and giving the impression to the public that there is a magic bullet, and this is your last hope?” said Shriprakash Kalantri, an epidemiologist in the west Indian state of Maharashtra.