Several great apes at the San Diego Zoo received two doses each of a COVID-19 vaccine in February, National Geographic reports. The lucky recipients are four orangutans and five bonobos, who were distracted with treats as they got their shots. One of the orangutans is Karen, the first ape to undergo open-heart surgery in 1994.

Ape vaccination is a welcome development at the San Diego Zoo, where a troop of eight gorillas tested positive for COVID-19 in January. The sick gorillas were symptomatic but have now recovered, according to the zoo. They’ll likely join their orangutan and bonobo compatriots in vaccination later in the spring. 

The vaccine the apes received is not one of the vaccines that have been authorized for humans. It was developed by a veterinary pharmaceutical company after the first recorded case of COVID-19 in a dog in February 2020. In addition to dogs and gorillas, minks, domestic cats, and big cats have also been infected by the virus.

After the vaccine was confirmed to be safe and effective for dogs and cats, Nadine Lamberski, chief conservation and wildlife health officer at the San Diego Zoo Wildlife Alliance, decided to start vaccinating the apes, National Geographic reports. 

Lamberski says it’s common to give vaccines to species that are different from the ones they were tested on because they’re developed for specific pathogens, not specific species. The apes haven’t had any adverse reactions, and they’re being tested for antibodies to see if the vaccine is working. Lamberski’s team will continue collecting and sharing data about the vaccine’s effectiveness as more apes are vaccinated.

Correction March 3rd, 6:42PM ET: An earlier version of this post referred to Nadine Lamberski as the chief conservation and wildlife health officer at the San Diego Zoo. She holds that position at the San Diego Zoo Wildlife Alliance, the zoo’s parent organization. We regret the error.