Pfizer Inc. is set to dominate the $20 billion market for COVID-19 pills next year as richer nations rush to purchase supplies, while less affluent countries will have to wait until early 2023 for generic-drug companies to produce large quantities, an analysis shows.

Pfizer, already pulling in huge profits from its COVID-19 vaccine, is expected to reap about $17 billion from sales of its experimental therapy Paxlovid in 2022, according to Airfinity Ltd. Merck & Co.’s molnupiravir will see about $2.5 billion in revenue next year, the London-based data company said.

Demand for the medications is poised to outpace supply as COVID-19 spreads around the globe and scientists question how well vaccines and antibody treatments will hold up against omicron and other variants that could arise. Rich countries’ purchases have fueled concerns that, after struggling to obtain vaccines, the less wealthy could be left behind once again, despite licensing agreements to widen availability of the drugs.