That will help to meet the continued need for vaccine supply in the US

As remarked by Pfizer CEO, Albert Bourla:

More doses to help expand protection in the US. Pfizer and BioNTech will deliver 200M more #COVID19 vaccine doses to the US by April 2022. We are very proud to be a long-term partner to the US government and to help ensure broad vaccine access across the country into next year.

The doses mentioned are expected to be delivered some time from October 2021 through to April 2022.