Vaccine major Serum Institute of India on Sunday rejected charges that AstraZeneca-Oxford's COVID-19 vaccine candidate has serious side effects and said it will seek damages in excess of Rs 100 crore for "malicious" allegations.

A 40-year-old Chennai-based business consultant, who was a volunteer for the third phase of the vaccine trial conducted by Serum Institute of India (SII), has alleged serious side effects, including a virtual neurological breakdown and impairment of cognitive functions and has sought Rs 5 crore compensation in a legal notice to SII and others, besides seeking a halt to the trial.

He was administered the shot at Chennai's Sri Ramachandra Institute of Higher Education and Research (SRIHER), one of the trial sites.

"The allegations in the notice are malicious and misconceived. While the Serum Institute of India is sympathetic with the volunteer's medical condition, there is absolutely no correlation between the vaccine trial and the medical condition of the volunteer," Serum Institute of India said in a statement.

The volunteer is falsely laying the blame for his medical problems on the COVID vaccine trial, it added.

"The claim is malicious because the volunteer was specifically informed by the medical team that the complications he suffered were independent of the vaccine trial he underwent. In spite of specifically being made aware of the same, he still chose to go public and malign the reputation of the company," Serum Institute said.

It is evident that the intention behind the spreading of such malicious information is an oblique pecuniary motive, it added.

"The Serum Institute of India will seek damages in excess of (Rs) 100 crore for the same and will defend such malicious claims," the statement said.

The Drugs Controller General of India and the institutional ethics committee at the implementation site are investigating if the adverse event as claimed to have been suffered by an Oxford COVID-19 vaccine trial participant in Chennai is related to the shot administered to him.

A law firm on his behalf has sent a legal notice to Director General, ICMR, Drugs Controller General of India, Central Drugs Standard Control Organisation, CEO AstraZeneca UK, CEO Serum Institute of India, Professor Andrew Pollard, Chief Investigator, Oxford Vaccine Trial and Vice-Chancellor of Sri Ramachandra Higher Education and Research.

Dr Samiran Panda, who heads the Epidemiology and Communicable Diseases (ECD) division of the ICMR, said the causal link, if any, of the serious adverse events with the investigational product is objectively assessed in any clinical trial following a pre-defined scientific pathway and within a stipulated period.

"Any hurried inquiry or inference is prone to be wrong. Both the institutional ethics committee and the DCGI are investigating the causal links, if any, between the adverse events and investigational product, which is an anti-coronavirus vaccine," Panda said.

The notice given on November 21 by the law firm said, "Our client states that he must be compensated, in the least, for all the sufferings that he and his family have undergone and are likely to undergo in future."

"He further states that he is still far from being all right and has to be under medical care for a long time to come. Therefore, for all the trauma he is undergoing and with an uncertain future in his health, he should be given a financial compensation of Rs. 5 crore within two weeks from the receipt of this notice," it added.

The notice also said that testing, manufacturing and the distribution of the vaccine should also be stopped immediately, "failing which he has no other option except to take appropriate legal action against all the concerned parties, who would be made responsible for all the costs and consequences".