SAN DIEGO (KSWB) — Several great apes at the San Diego Zoo are now vaccinated against COVID-19 thanks to a first-of-its-kind vaccine made strictly for animals.

The San Diego Zoo Wildlife Alliance said four orangutans and five bonobos are vaccinated against SARS-CoV-2 after veterinarians there received a limited supply of a vaccine called Zoetis, which is designed only for animals.

The great apes were vaccinated in February, a month after a gorilla troop caught COVID-19 at the San Diego Zoo Safari Park in Escondido. Park staff said the gorillas were infected with the B.1.429 variant of the coronavirus, which had been prevalent in California.

The troop was under close observation following the diagnosis with some gorillas showing symptoms, including mild coughing, congestion, nasal discharge and intermittent lethargy. But the gorillas have recovered well, officials say.

A spokesperson said the previously infected gorillas didn’t receive the vaccine because experts believe they developed their own immune response, while those that did receive the vaccine didn’t show any adverse effects.

“I know, like a good parent, the zoo will do everything it can to protect the health and well-being of the animals in its care,” said Bill Toone, founder of ECOLIFE Conservation. “For those animals that will stay in the zoo’s collection, getting them vaccinated and doing everything they can to protect them is absolutely essential.”

However, he does have a concern.

“One of my concerns is that if there’s animals for example that are part of a population that’s being considered for reintroduction, do we want to create animals that we have artificially created an immune response in them, and we don’t know how that reacts in wild populations,” Toone said.

The San Diego Zoo Wildlife Alliance said it doesn’t plan to release the vaccinated animals into the wild. Instead, animal experts hope to better understand how the virus affects great apes and how to curb transmission.