Pfizer Inc. and BioNTech SE said they are partnering with a Brazilian pharmaceutical company to help manufacture their Covid-19 vaccine in Latin America, which could help meet growing demand for the shot in the region.

Eurofarma will produce at least 100 million doses annually for distribution in the region, Pfizer and BioNTech said Thursday.

The doses will be in addition to those reaching Latin America through distribution channels such as Covax, the global initiative intended to get vaccines to low-income countries, and donations by the U.S., the companies said.

Financial terms of the deal weren’t disclosed.

Pfizer and BioNTech said manufacturing will begin next year, after the companies have completed a lengthy process known as technology transfer, in which they provide Eurofarma with top-secret information about the vaccine, manufacturing know-how and other key details.

The Eurofarma deal is the first in Latin America for the shot from Pfizer and BioNTech, which along with other vaccine makers have been under pressure to increase supply for poorer countries. South Africa and other countries with tight supplies have proposed temporarily waiving patent protections so they can make the shots. Vaccine makers have opposed the measure, saying a technology transfer is a long and complex process and there is limited capacity.

“We will continue to explore and pursue opportunities such as this to help ensure that vaccines are available to all who are in need,” said Pfizer Chief Executive Albert Bourla.

Latin America is slowly overcoming vaccine-supply problems, and vaccinations have risen sharply.

Supply concerns could be renewed, though, should more countries prepare to administer booster shots to maintain protection against the virus. The U.S. last week recommended additional shots for adults starting next month for people vaccinated from messenger RNA vaccines such as Pfizer’s.

Latin America, home to about 8% of the world’s population, accounts for roughly a third of global deaths from the pandemic, according to Johns Hopkins University.

The Pfizer-BioNTech vaccine involves a new gene-based technology called mRNA. Health authorities have confronted limited supplies as companies increase manufacturing. Some of the steps have been tough to scale up quickly, in part because they haven’t been performed before, according to manufacturing experts and the companies.

The Biden administration announced that Americans who have been fully vaccinated with a two-dose regimen against Covid-19 should receive a booster, citing the threat from the highly contagious Delta variant. WSJ breaks down what you need to know. Photo: Hannah Beier/Reuters The Wall Street Journal Interactive Edition

Eurofarma, based in São Paulo, will receive drug products from the U.S. and then perform a standard manufacturing step known as fill-finish, in which vials are filled with vaccines, capped and readied for shipment.

“At such a difficult time as this one, being able to share this news fills us with pride and hope,” said Eurofarma President Maurizio Billi.

Pfizer and BioNTech say they have shipped more than 1.3 billion doses to more than 120 countries and territories around the world. The companies say they can produce about three billion doses this year and four billion next year.

Other vaccine makers, including Moderna Inc. and AstraZeneca PLC, have also turned to outside manufacturers to increase production.

Pfizer and BioNTech have struck manufacturing partnerships with rival drugmakers such as Novartis AG as well as other companies such as Thermo Fisher Scientific Inc. Pfizer and BioNTech said the manufacturing network for the vaccine now spans four continents and more than 20 plants.

Write to Jared S. Hopkins at jared.hopkins@wsj.com