The world's COVID-19 vaccine makers are rapidly ramping up production and expressed optimism Tuesday that the U.S.

John Young, chief business officer at Pfizer, said at a hearing before the House Committee on Energy and Commerce that his company will have provided 120 million doses by the end of March and reach 300 million by the end of July.

That's enough for 150 million Americans, and Young said the company is working to ensure safety and effectiveness for children.

Stephen Hoge, president of Moderna, said his company also hopes to be deliver 300 million doses by the end of July.

Richard Nettles, Johnson & Johnson’s vice president of medical affairs, said if his company wins Food and Drug Administration approval for emergency use, J&J hopes to supply 100 million doses of its single-dose vaccine by the end of June.

Last week's power crisis prompted shipping delays, canceled appointments and destroyed more than 900 doses of the vaccine across the state. .

â–ºFive vaccine makers are testifying today before a House oversight committee investigating the wobbly rollout of COVID-19 vaccines.

has more than 28.1 million confirmed coronavirus cases and 500,200 deaths, according to Johns Hopkins University data

The global totals: More than 111.7 million cases and 2.47 million deaths. More than 75.2 million vaccine doses have been distributed in the U.S