Pfizer said it expects there could be a long-lasting need for COVID-19 vaccines, to combat new virus variants that emerge and to "boost" peoples' waning immune responses.
The Pfizer vaccine is produced in Belgium and the European Commission said on Friday it had agreed a plan to control exports of vaccines from the European Union, including to Britain.
With the assurances of both the EU and Belgian Ambassadors, the COVID-19 immunisation plan is expected to proceed according to plan.
The document, which was prepared for a virtual meeting of Chancellor Angela Merkel with the 16 state premiers and representatives of pharmaceutical companies and the European Union later on Monday.
"BioNTech/Pfizer will deliver 75 million of additional doses in the second quarter of the year - and up to 600 millions in total in 2021," von der Leyen wrote on Twitter.
President Joe Biden has pledged to have 100 million people vaccinated within his first 100 days -- but the rollout began slowly under former President Donald Trump.
A high bar has been set by two authorized vaccines from Pfizer/BioNTech and Moderna, which were around 95% effective in preventing symptomatic illness in pivotal trials when given in two doses.
J&J's main goal was the prevention of moderate to severe COVID-19, and the vaccine was 85% effective in stopping severe disease.
Pfizer and Biontech vaccine deliveries, including to Switzerland, have been impacted as they temporarily slow production at a plant in Puurs, Belgium, in preparation for boosting its capacity.
"Sanofi will provide BioNTech access to its established infrastructure and expertise to produce over 125 million doses of COVID-19 vaccine in Europe", Sanofi said in statement.
The WHO signed an advance purchase agreement with the American pharmaceutical, where it will receive at least 40 million doses of the drug.
It also anticipates another 50 million doses from UK-based pharmaceutical Oxford-Astrazeneca. As per the existing agreement with the company, the shipment will be made in first quarter of the year.