The Cincinnati Zoo said 80 of its animals have received two doses of a Covid-19 vaccine designed for veterinary use.
In a news release, the zoo said Monday that it has been vaccinating big cats, great apes, red pandas, goats, giraffes, river otters, skunks, bearcats and some domestic dogs and cats.
The zoo said that technicians and handlers worked for weeks to get the animals "comfortable with everything that they would see and feel when they got the injections" and that most were administered without anesthesia.
The zoo's director of animal health, Dr. Mark Campbell, said in the release, "We were concerned that the fresh memory of the first injection would make animals less willing to offer a shoulder or thigh for the second round, but they did!"
Campbell said the success "is 100% due to the strong relationships these animals have with care staff and our animal health team."
The remaining animals will get their second doses in the next two weeks, the zoo said.
Since the start of the coronavirus pandemic, Covid has spread among certain mammals, like big cats, great apes and minks, in zoos and farms around the world.
Last month, the National Zoo in Washington, D.C., found that nine of its big cats were infected with the coronavirus after they displayed symptoms like coughing, sneezing and lethargy. It said at-risk animals would soon be vaccinated.
Zoo Atlanta reported an outbreak among a troop of western lowland gorillas last month.
The experimental veterinary vaccine being used in Cincinnati and at other U.S. zoos is made by Zoetis, one of the largest animal pharmaceutical manufacturers in the country.
Christina Lood, a spokesperson, said scientists at the company "immediately" began working on a veterinary coronavirus vaccine after Hong Kong reported infections in dogs early in the pandemic.
Lood said it was the outbreak at Danish mink farms that led the Agriculture Department, which regulates veterinary vaccines, to take notice.
"The USDA said, 'OK, now we want a vaccine for mink potentially, so we kind of pivoted to mink last fall, and the San Diego Zoo was kind of watching all this," she said.
After an outbreak among gorillas in San Diego early this year, the zoo requested experimental access to the Zoetis vaccine. Lood said that Zoetis donated its leftover doses from previous safety studies and that the zoo administered them to nine of the great apes in March.
The vaccine has been universally well tolerated by animals, Zoetis reported, but the coronavirus has continued to spread among zoo animals in San Diego and around the world.
In July, the San Diego Zoo reported that an unvaccinated snow leopard had tested positive for Covid after it displayed symptoms.
By summer, after more coronavirus outbreaks among zoo animals, Zoetis said it had received even more requests for access to its experimental vaccine, and it manufactured a new batch, the first of which went to the Oakland Zoo in late June, Lood said.
Isabella Linares, a marketing associate with the Oakland Zoo, said that of the more than 100 animals designated "at-risk" by specialists — including primates, large cats, river otters and bears — 37 have yet to be vaccinated.
One reason not all animals have been vaccinated is that participation is "voluntary," Linares said.
"The tigers are trained voluntarily to present their backside to us so we can give them the vaccine," she said, saying most are already trained to do so from previous vaccinations. But she said some animals, like one of the zoo's leopards, need more time to learn.
Just one animal at the Oakland Zoo, a brown bear, had post-vaccination side effects — tenderness at the injection site — and none of its vaccinated or unvaccinated animals have tested positive for the coronavirus.
"We are really lucky," Linares said, noting that an unvaccinated African lion at the Honolulu Zoo died recently after it tested positive for the virus.