India has detected 25 cases of the emergent Omicron variant of the coronavirus and all have shown mild symptoms, the health ministry said yesterday, adding that there was no immediate plan to authorise vaccine boosters.

Vaccine supplies have surged in India in recent months thanks to the Serum Institute of India (SII), which now plans to halve the monthly output of its version of the AstraZeneca vaccine as demand has crashed.

The SII and other Indian drugmakers such as Dr. Reddy's Laboratories, which distributes Russia's Sputnik vaccine, have lobbied the government to approve booster shots in a bid to lift sales.

Senior health official Vinod Kumar Paul told a news briefing that government experts were studying data on boosters but "our emphatic view...is to (first) cover every adult with (just) the primary two doses."

The government has said this target can be achieved by January.

India has not considered authorising booster doses yet as many in the country have been naturally infected and the government believes two vaccine doses offer sufficient protection for now, three informed sources told Reuters late last month.

Around 87% of India's adults, estimated at 939 million people, have received at least one dose of a vaccine and 54% of them have received the full two. Inoculations for those under the age of 18 years have not started.