Just over three months ago, in December 2020, research found that monkeys and apes from Africa and Asia are susceptible to the SARS-CoV-2 virus. At the time, there was particular concern for endangered gorillas because the disease could have a detrimental effect on their small population size, and for captive chimpanzees living in sanctuaries who are in close contact with humans.

Then in January, it was reported that a troop of eight captive gorillas living at the San Diego Zoo tested positive for COVID-19. While the gorillas made a full recovery, this incident showed that gorillas can, in fact, contract and become sick from COVID-19. 

On March 3, however, there was good news for our primate cousins: great apes living at the San Diego Zoo received experimental COVID-19 vaccines. Four orangutans and five bonobos were vaccinated, making these nine animals the only non-human great apes to be immunized in the world. There are three leftover doses, which will be given to the three gorillas living at the zoo who did not have COVID-19 in January. 

This specific vaccine cannot be used for humans. It was developed by Zoetis for dogs and cats, among ongoing debate as to whether such a vaccine would be useful. While the vaccine used on the great apes in San Diego was not specifically designed for them, Zoetis provided an emergency supply of the vaccine for this specific use. The idea of using a vaccine for one animal to inoculate another is not new. In fact, the influenza vaccine developed for humans is given to great apes in zoos every year and researchers are working to develop cross-species vaccines to treat other diseases like malaria. 

While there is still relatively little known about how COVID-19 affects the animal kingdom, scientists are also worried about whether the virus could gain foothold in an animal population, and then reemerge and infect humans again. While it remains unclear whether the vaccine could (or should) be used to inoculate wild populations, the immunization of captive populations is certainly a step towards a safer world for all animals.