Moderna and Pfizer plan to significantly boost vaccine shipments to the U.S. government by this spring, according to written testimony from company executives released Tuesday ahead of a House committee hearing on vaccines.

Where it stands: Pfizer expects to increase its weekly vaccine delivery from 4-5 million doses at the start of February to more than 13 million doses by mid-March, said John Young, Pfizer's chief business officer.

• Moderna is working to deliver more than 40 million doses per month, doubling its current shipment, and aims to ship another 100 million doses by the end of May, said Moderna president Stephen Hoge.

Of note: Both companies are studying potential booster shots in response to emerging coronavirus variants. Their vaccines have shown to be effective against the highly transmissible strains first seen in the U.K. and South Africa.

Pfizer is also studying booster effects in trial participants who have been fully vaccinated, Young said.

• Moderna hopes to provide vaccinations to adolescents by the fall and is currently testing its vaccine's safety for children ages 12 to 18.

Be smart: The more Americans that are fully vaccinated, the faster that herd immunity will be reached — making it more difficult for the virus to spread.

What's next: Executives from the companies are slated to testify before the Energy and Commerce Committee Tuesday morning.

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