Health officials are buying millions of vaccines for Latin America.

The Pan American Health Organization has struck a deal with the Chinese manufacturer Sinovac to purchase millions of Covid-19 vaccines for countries in Latin America and the Caribbean as part of an effort to make more shots available in a region where access has been very unequal.

The agency, part of the World Health Organization, is negotiating with two other manufacturers and expecting to announce new deals soon, Dr. Jarbas Barbosa, its assistant director, said at a news conference Wednesday.

Sinovac has offered to sell 8.5 million doses this year and an additional 80 million in 2022, he said. Countries in the region that want the vaccine will have to buy it from the health organization.

“This is a purchase, it isn’t a donation,” Dr. Barbosa said, noting that the Inter-American Development Bank is offering loans to countries that need them.

The direct purchases begin at a time when, on average, only 35 percent of the population of Latin America and the Caribbean has been fully vaccinated against Covid-19, Dr. Carissa F. Etienne, the director of the agency, said, noting that the coverage has been very unequal.

While some countries, including Chile and Uruguay, have fully vaccinated over 70 percent of their populations, she said, others have yet to reach the 20 percent mark. Those countries are: the Bahamas, Grenada, Guatemala, Haiti, Honduras, Jamaica, Nicaragua, St. Lucia, St. Vincent and the Grenadines and Venezuela. Haiti is a particularly dire case, she said, with less than 1 percent of the population fully vaccinated.

The health organization is also working to expand vaccine manufacturing in the region, and last week announced that a facility in Brazil and another in Argentina will receive technical support to begin production of messenger RNA vaccines, the type used in the Pfizer-BioNTech and Moderna shots.

But for the time being, “vaccine donations remain the fastest way to support countries in our region,” Dr. Etienne said.