A female ring-tailed lemur named Charlie this week became the first animal to receive a special COVID-19 vaccination at the Philadelphia Zoo.

Charlie was part of a group of 10 animals, including four other ring-tailed lemurs, four western lowland gorillas, and a Sumatran orangutan, to get their shots.

In the coming weeks, 113 animals at the zoo will receive the two-dose vaccine from a shipment of 240 doses provided by Zoetis, a former subsidiary of Pfizer headquartered in New Jersey that develops drugs for animals.

Nationally, there have been documented cases of zoo animals becoming sick from COVID-19, including gorillas, snow leopards, and tigers at the San Diego Zoo and Safari Park, and just last week at Zoo Atlanta with western lowland gorillas testing positive.

There have been no confirmed cases at the Philadelphia Zoo, but a couple of instances of gorillas showing possible mild symptoms, prompting tests that turned out negative, said Keith Hinshaw, the zoo’s director of animal health.

“When it’s cold season, you’ll see gorillas get colds. When it’s allergy season, you’ll see gorillas get allergies, and so on,” Hinshaw said. “There’s been a couple of times this year where we had gorillas who had a runny nose or a cough, or something like that.”

But so far, he said, “we have not found any coronavirus in any cases here.”

Earlier this year, Zoetis announced it was providing more than 11,000 doses of its vaccine to zoos and other organizations. Zoos are not required to publicly reveal if they are vaccinating their animals for COVID-19, but ones that have made announcements include those in Oakland, San Diego, Denver, Detroit, Atlanta, and now Philadelphia.

Officials at the Philadelphia Zoo said they are designing their vaccination schedule based on factors like prioritizing higher-risk animals, vaccinating animals trained to receive injections voluntarily, and identifying animals who are already scheduled for routine physical exams.

Animals at the Philadelphia Zoo already get other vaccinations. Gorillas and orangutans get annual flu shots. Big cats are given yearly shots for distemper, a highly contagious viral disease.

“The tigers, lions, some of the bears, the gorillas, orangutans, and so on, they’re all trained that if they come up, press their shoulder or hip against the mesh and let us give them an injection or let the keeper give them an injection, then they get a treat in return as a reward,” Hinshaw said.

After the Zoetis vaccination became available, Philadelphia Zoo officials approached the company about receiving doses. Zoetis handles the government approvals because the vaccine is experimental, Hinshaw said. Each use needs to be authorized by the U.S. Department of Agriculture and an equivalent state authority.

Any adverse reactions from the vaccine need to be reported immediately, Hinshaw said, and so far none have been documented.

There is no impending expiration date for the vaccine because it does not contain a fragile live virus, but Zoetis recommended that once a vial was opened, its contents should be used within 24 hours, Hinshaw said.

Each vial contains 10 doses, so the zoo vaccinated 10 animals Tuesday, and plans to proceed with vaccinating 10 animals at a time, he said.

To guard against the transmission of the virus, animal keepers wear face masks, face shields, and gloves. Zoo staffers are encouraged to be vaccinated themselves against COVID-19.

“Anything we can do to prevent the virus replicating in animals … is a plus,” he said. “Because every time it replicates is a chance for that virus to mutate, and you can get another variant, [a] strain that might be worse than what you already have. So vaccines are important for animals and humans.”