Any significant adverse effect is unlikely if the second dose of a different COVID-19 vaccine is administered, but reaching a firm opinion on this will need more scrutiny and understanding, the Centre said on Thursday.

It, however, clarified that both doses administered to an individual should be of the same vaccine as per the existing protocol.

The clarification comes following reports that health workers in Uttar Pradesh's Siddharthnagar district administered Covaxin to 20 villagers who had been given Covishield in the first dose.

NITI Aayog member (Health) V K Paul said the incident needed to be investigated.

"Any significant adverse effect is unlikely if the second dose of a different COVID-19 vaccine is given. In fact, there is a narrative that is going on that taking doses of two different vaccines can lead to stronger immunity... but for a firm opinion, more scrutiny and understanding will be required," he said at a presser.

Commenting on the UP incident, he said, "Even if it has happened, it should not be a cause of concern for the individual, but I urge all health workers to give second dose of the same vaccine."

The incident was reported from the primary health centre in Barhni where people from Audahi Kala and another village received Covaxin shots on May 14.