It has obtained supplies of Nuvaxovid from the Novavax company. It is a vaccine that protects against serious complications of the pandemic without being based on mRNA.
Developed by Moderna and the team of Pfizer and BioNTech, the new so-called bivalent shots combat the BA.1 version of Omicron and the original virus first detected in China.
Pfizer said it has some doses ready to ship immediately and can deliver up to 15 million doses by September 9.
US President Joe Biden's administration expects to run out of federal funding for buying and distributing COVID-19 vaccines by January.
Moderna said in a statement that Pfizer and BioNTech infringed on patents filed between 2010 and 2016 that covered its mRNA technology.
The European Medicines Agency (EMA) is recommending that Novavax should start putting a warning label on their COVID-19 vaccines due to a small number of reported cases of heart inflammation.
New study by Yale, UNC, shows that peak antibody levels achieved by getting vaccinated with an mRNA vaccine exceed those gained from natural infection.
President Joe Biden's administration plans to roll out the vaccines to the under-5 age groups as early as next week.
Moderna released trial data in March showing that its vaccine was safe and generated a similar immune response in young children as for adults.
No safety issues have been identified, Moderna said about the lots that were distributed in Norway, Poland, Portugal, Spain and Sweden in January.