The Serum Institue of India (SII) has put on hold trials of potential COVID-19 vaccine produced by British pharmaceutical company AstraZeneca following a notice issued by the Drugs Controller General of India (DCGI).

The trials will be restarted once the British drugmaker restarts them.

"We are reviewing the situation and pausing India trials," Serum stated.

The DCGI V.G. Somani has asked SII about the details of the suspension of COVID-19 trials overseas after reports of unexplained illness in a study participant forced AstraZeneca to paused trials of its experimental coronavirus vaccine.

She asked for an explanation from SII as to why the trials should not be suspended in India until and unless patient safety is established. She warned the company of strict action if it failed to provide a valid explanation.

SII has stated that it paused trials of its experimental coronavirus vaccine.

AstraZeneca Plc on Tuesday said it has paused a late-stage trial of one of the leading COVID-19 vaccine candidates after an unexplained illness in a study participant.

The study is testing a COVID-19 vaccine being developed by AstraZeneca and the University of Oxford researchers at various sites, including the United Kingdom, where the illness was reported.

The nature of the case and when it happened were not detailed, although the participant is expected to recover, according to Stat News, which first reported the trial was halted due to a "suspected serious adverse reaction." The U.S. Food and Drug Administration defines that as an adverse event in which evidence suggests a possible relationship to the drug being tested.

The suspension of the trial has impacted other AstraZeneca vaccine trials - as well as clinical trials being conducted by other vaccine makers, which are looking for signs of similar reactions, Stat said.

At present, SII was progressing the second and third-phase studies of the vaccine candidate at 17 trial sites.

The drugs regulator had in August given Serum approval to run Phase II/III clinical trials on the leading COVID-19 vaccine candidate to determine its safety and immunogenicity.