Nine great apes after been vaccinated against the coronavirus at the San Diego Zoo in California.
Officials have said that four orangutans and five bonobos received COVID-19 injections in January and February.
It came after several gorillas at the zoo became infected with the virus, likely from contact with a zookeeper who tested positive for the virus.
Three bonobos and a gorilla are also expected to receive the experimental COVID-19 vaccine for animals, according to AP.
There were eight western lowland gorillas in the zoo's Safari Park who became infected with the virus earlier this year but the gorillas have recovered, according to San Diego Zoo.
One of the gorillas, Winston, who is older, developed pneumonia and heart disease.
The zoo had announced in January that it was provided with a limited supply of "a recombinant purified spike protein vaccine" for animals amid the COVID-19 outbreak among the gorillas.