Pfizer Inc said on Tuesday it expected to generate $15 billion, or about a quarter of its total revenue this year, from the sale of its COVID-19 vaccine that it has developed with German partner BioNTech.

The drugmaker is striving to deliver two billion doses of the vaccine in 2021 at a breakneck pace as countries rush to sign supply deals in an effort to control a pandemic that has killed over 2 million people globally.

Pfizer has supplied 65 million doses globally and 29 million doses to the United States as of Jan. 31. It said it expects to supply 200 million doses to the U.S. government by the end of May.

To achieve the goal, it will have to deliver an average of around 10 million doses per week, which is more than double the rate Pfizer and BioNTech delivered doses to the United States through the end of January, according to a Reuters calculation.

Its supply, however, has faced delays in parts of Europe due to changes in manufacturing processes in order to boost production. BioNTech said on Monday the companies were back on track to meet their European timeline.

The vaccine was among the first to be authorized for emergency use in the United States and several other countries.

Pfizer forecast 2021 sales of between $59.4 billion and $61.4 billion, with the vaccine sales projected to contribute nearly 25% of the sales.

In contrast, 2020 sales from its best-selling pneumonia vaccine Prevnar 13 represented nearly 14% of Pfizer’s sales of $41.91 billion.

The company now expects full-year adjusted earnings of $3.10 to $3.20 per share, up from its prior forecast of $3 to $3.10 per share.

Excluding items, Pfizer earned 42 cents per share, but missed market expectation of 48 cents per share, according to IBES data from Refinitiv.