A study that alleged that anti-malarial drug hydroxychloroquine increased the risk of death in Covid-19 patients was retracted over data concerns. The findings of the study were published in the medical journal The Lancet on May 22.

The findings had led the World Health Organization to temporarily suspend trials of hydroxychloroquine for treatment of the coronavirus. The study had said that hydroxychloroquine could increase patient mortality rate in hospitals. It also found that those administered the drug showed a higher frequency of arrhythmia, or irregular heartbeat.

Three of the study’s authors on Thursday said they could no longer vouch for its veracity as the healthcare firm that supplied the records would not allow an independent review of its dataset. Mandeep Mehra, a Harvard University professor who led the study, said in a statement that they had tried to arrange for a third-party peer review of the data, but Surgisphere had refused to co-operate. The other two authors who issued the joint statement are Frank Ruschitzka of the University Hospital Zurich and Amit Patel of the University of Utah. “We deeply apologise to you, the editors, and the journal readership for any embarrassment or inconvenience that this may have caused,” the three said in their statement.

The study’s fourth author Sapan Desai, who is also the chief executive officer of Surgisphere, told The Guardian that transferring the data would “violate client agreements and confidentiality requirements”. He, however, said he would co-operate with an independent audit.

Use of hydroxychloroquine to prevent and treat Covid-19 has been a focus of public attention. India has been using the drug extensively and has also exported it to many foreign countries, including the United States. On May 22, the Ministry of Health and Family Welfare revised its advisory on the use of hydroxychloroquine as a prophylactic against the coronavirus. The ministry’s decision came after the National Task Force, constituted by the Indian Council of Medical Research, reviewed and recommended the use of the drug for coronavirus patients.

United States President Donald Trump has also promoted the drug despite the absence of evidence to prove its effectiveness and last month said he was taking it himself in hopes of preventing the infection. In April, he lauded Indian Prime Minister Narendra Modi’s decision to supply the drug to the United States.

As of now, there’s no evidence that any drug effectively works to reduce the mortality among Covid-19 patients, said WHO officials.

On Wednesday, a study published in the New England Journal of Medicine said hydroxychloroquine failed to prevent healthy people, who were exposed to the novel coronavirus, from getting the infection. It was the first major randomised clinical trial looking at whether the medication might be useful as a prophylactic. The findings came on the same day the World Health Organization said that it will resume clinical trials of the drug.