Philadelphia, Pennsylvania - 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 each 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.

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There have been no confirmed cases at the Philadelphia Zoo, but a couple 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.

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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.