WASHINGTON, Dec 19: The US pharma Moderna has discarded 4,00,000 doses of its covid vaccine after a filtration issue compromised product quality during the final stages of manufacturing, it has been reported.

The 400,000 doses which were not placed in the vials are just a drop in the bucket with Moderna planned to manufacture 1 b in the new year, said Moncef Slaoui, Operation Warp Speed chief scientific adviser.

He said it is production line problem and will not affect the targets. Such challenges are expected while pursuing a complex manufacturing process like Moderna's mRNA vaccine, Moncef told Bloomberg News.

Moncef is a top vaccine expert having spent three decades at the Glaxo vaccine unit. He said, "Everything is going on smoothly. There is no problem."

Moderna has 20 m doses to be distributed in the US in December. It said it will manufacture 125 m doses in the first quarter of 2021 out of which 85 m to 100 m doses would be available in the US and 15 m to 25 m available outside the country. It plans to manufacture a total of 500 m to 1 b doses in 2021.

All the vaccines being developed in the world currently need two doses separated by two-three weeks time gap, except Johnson & Johnson.