Four orangutans and five bonobos in the United States received two doses of an experimental vaccine originally developed for dogs and cats.

Nine great apes at the U.S. San Diego Zoo – four orangutans and five bonobos – have made veterinary history in the past few weeks as the world’s first nonhuman primates known to be vaccinated against COVID-19, zoo officials said Thursday with.

One of the recipients was a 28-year-old Sumatran orangutan woman named Karen who made headlines at the zoo when she became the first monkey to undergo open heart surgery in 1994.

Each of the nine animals received two doses of an experimental vaccine originally developed for dogs and cats, with the monkeys showing no side effects and all doing well, zoo spokeswoman Darla Davis said in an email to Reuters news agency .

Zoo officials filmed concerns about animal welfare after a troop of eight gorillas at the adjoining San Diego Zoo Safari Park contracted COVID-19 in January. This was the first known transmission of the virus to great apes.

The health of the gorillas, including a 48-year-old silver-backed male named Winston who suffered from pneumonia and heart disease, has since improved and they appear to be on the way to a full recovery, Davis said.

Winston has been treated with a variety of drugs, including coronavirus antibody therapy for non-humans.

The gorillas were not vaccinated because veterinarians assumed that their immune systems had already developed antibodies against the virus. It was believed that they got the disease from an asymptomatic worker.

Easiest to vaccinate

The orangutans and bonobos selected for immunization were among the great apes in the zoo considered most at risk from the virus and the easiest to vaccinate. The staff vaccinated the animals by distracting them from the needle with treats.

The zoo’s staff began giving the shots to some of the animals in January and continued through February, with the last being given in March, Davis said.

The vaccine developed by the veterinary drug company Zoetis has not been tested on monkeys.

Using vaccines between species is not uncommon, and monkeys at the zoo are getting vaccines against human flu and measles, according to Nadine Lamberski, senior conservation and wildlife officer for the San Diego Wildlife Alliance, the organization that owns the zoo and safari park.

She said the nine great apes were the first non-human primates known to have received any type of COVID-19 vaccine.

“That’s not the norm. In my career, at the beginning of the process, I didn’t have access to an experimental vaccine and I wasn’t overwhelmed by an overwhelming desire to use one, ”Lamberski told National Geographic magazine in a separate interview.