LONDON, May 20 (Xinhua) -- A British professor has warned that U.S. President Donald Trump's advice about taking an anti-malarial drug to protect against the novel coronavirus "could kill vulnerable people", the British newspaper Liverpool Echo reported on its website.

Trump told reporters on Monday that he has taken hydroxychloroquine which he said could be a potential treatment for coronavirus, on a daily basis, despite warnings that it can cause heart problems.

"A couple of weeks ago, I started taking it," he said. "All I can tell you is, so far I seem to be OK."

Calum Semple, professor in child health and outbreak medicine at the University of Liverpool, said Tuesday that he doesn't recommend the medicine particularly for those people most at risk of severe disease, issuing a strong rebuttal of Trump's suggestion.

"Chloroquine is absolutely contra-indicated for people who have diabetes and are taking specific anti-diabetes drugs, it can cause a profound drop in the blood sugar, and that can lead to death, OK? So let's just be absolutely clear about this, this is not something that we're recommending particularly for those people most at risk of severe disease," Semple was quoted by the Liverpool Echo as saying.

"It also causes problems for people with liver disease and the elderly, that have got poor kidney function, they're at high risk of side effects from chloroquine as well, so I'm sorry, I'm very disappointed to hear this," Semple added.

The U.S. Food and Drug Administration (FDA) warned in late April against the use of hydroxychloroquine or chloroquine for COVID-19 "outside of the hospital setting or a clinical trial due to risk of heart rhythm problems."

"Hydroxychloroquine and chloroquine have not been shown to be safe and effective for treating or preventing COVID-19," the FDA said in a release. "They are being studied in clinical trials for COVID-19."

Separately, a study released by the U.S. Veterans Health Administration last month suggested the drug was ineffective in treating patients with COVID-19 and found that the two primary outcomes for patients treated with the drug were the need for mechanical ventilation and death.