NEW YORK - The pace of Moderna Inc's COVID-19 vaccine production is unlikely to speed up markedly in the next few months, though the US drugmaker expects output to have increased significantly by 2022, its chief executive said on Wednesday.

The US government has urged Moderna to speed up its production and delivery schedules for the shots after it temporarily halted the shipment of Johnson & Johnson's vaccine amid reports that six women developed rare blood clots after getting the shot.

"Adding big chunks of capacity takes time," Chief Executive Stephane Bancel said during a Wednesday investor call.

He added however that he expects recently announced investments in manufacturing capacity to "very materially" increase Moderna's 2022 production.

Moderna is still on track to deliver between 700 million and one billion doses globally in 2021, Bancel said.

White House COVID-19 coordinator Jeff Zients said on Tuesday that the United States has more than enough vaccine from Pfizer Inc and Moderna to keep up the pace of vaccinations with or without J&J's doses.

Moderna said earlier this month that it is on track to meet delivery targets in Europe, which has also halted the rollout of J&J's vaccine.

"We are going to reassess what we are doing with our manufacturing capacity based on what is happening in the marketplace and what is happening with other vaccines," Bancel said.

Moderna is testing the use of smaller doses for booster shots that could result in greater production capacity in the future, as more people begin getting boosters rather than first-time inoculations, he added.

Reuters