Motorists ride past the entrance of India's Serum Institute in Pune. Photo: AFP/Punit Paranjpe

The world’s biggest vaccine maker, India’s Serum Institute, has urged other countries to be “patient” about it supplying anti-coronavirus shots, saying it has been instructed to prioritize its home market.

“Dear countries & governments, as you await #COVISHIELD supplies, I humbly request you to please be patient,” Serum chief Adar Poonawalla tweeted on Sunday.

“@SerumInstIndia has been directed to prioritize the huge needs of India and along with that balance the needs of the rest of the world. We are trying our best.”

Serum, from its sprawling facility in Pune in western India, is producing hundreds of millions of doses of the AstraZeneca vaccine.

Many countries around the world, particularly poorer nations, are relying heavily on the company for supplies of the vaccine, and it has already shipped millions of doses abroad.

The Serum Institute also plans to supply 200 million doses to Covax, a World Health Organization-backed effort to procure and distribute inoculations to poor countries.

Poonawalla did not say who had told the firm to prioritize India, or whether the instructions were new.

India’s aim of inoculating 300 million people by July is falling well behind schedule with just over 11 million shots given so far.

The problems, however, are thought to lie more with not enough people coming forward for the vaccinations rather than problems with supplies of the shots.