Caribbean nations struggle with vaccination efforts.

In Guatemala, shortages of syringes have slowed vaccination efforts. In Haiti, logistical and security challenges after the devastating Aug. 14 earthquake have contributed to making it the country with the lowest vaccination coverage in the world.

And across the Caribbean, countries are grappling with unequal distribution of doses and vaccine hesitancy, World Health Organization officials warned today in an online news conference.

An “important challenge that the Caribbean is facing — English-speaking countries and French- speaking countries and territories — is vaccine hesitancy,” said Dr. Sylvain Aldighieri, the Covid-19 incident manager at the Pan American Health Organization, which is part of the W.H.O.

“Even if some territories of the Caribbean are leading the regional effort in terms of vaccination coverage, we can say that the vaccine uptick is suboptimal in most of the Caribbean countries,” he said.

The W.H.O. has set a goal of having every country in the world vaccinate at least 40 percent of its population by the end of the year. Four of the six countries in the Americas that have yet to reach the 20 percent threshold are in the Caribbean: Haiti, Jamaica, St. Vincent and the Grenadines, and St. Lucia. The other two — Nicaragua and Guatemala — are in Central America.

“Across all these countries, vaccine availability due to unequal distribution of doses has been a central challenge,” said Dr. Carissa F. Etienne, the Pan-American agency’s director.

But several of the countries are also “facing their own unique barriers,” she added, like the shortage of syringes in Guatemala.

At the same time, Jamaica has had to cope with supply delays.

Haiti, where the August earthquake killed at least 2,200 people, has fully inoculated less than 1 percent of its population.

“The sociopolitical situation in Haiti is still tense, and that has negatively impacted” vaccination efforts, said Ciro Ugarte, the Pan-American agency’s director of health emergencies.

Countries in Latin America and the Caribbean receive vaccines through bilateral agreements with manufacturers as well as through the United Nations-backed Covax program and donations from countries with excess doses. The Pan-American agency has also sealed deals for countries to buy millions of vaccine doses from China’s Sinopharm and Sinovac, as well as from AstraZeneca.

Although the numbers of Covid cases in much of Latin America and the Caribbean are declining, several islands in the Caribbean are seeing increases.

Barbados, for example, is reporting the highest number of infections and deaths since the pandemic started, said Dr. Etienne, the agency’s director. The Dominican Republic, Haiti, the Cayman Islands, Antigua and Barbuda, and Anguilla are also reporting increases in cases.

“In the eastern Caribbean, health services have been — or are still — overwhelmed by the influx of patients requiring hospitalization,” Dr. Aldighieri said. He also noted that the situation was a sharp contrast to last year, when most of the Caribbean island countries were largely able to avoid widespread transmission of the virus.

Despite vaccine hesitancy, 39 percent of the population across Latin America and the Caribbean have been fully vaccinated against Covid-19, Dr. Etienne said. That is sharply higher than in Africa, where less than 5 percent of the population has been fully vaccinated, according to the Africa Centers for Disease Control and Prevention.

As more vaccines start to flow to the region, though, it’s important for countries “to make the necessary preparations so these doses can be used as quickly as possible,” Dr. Etienne said.