There's strong evidence to support that SARS-CoV-2 — the pathogen which causes COVID-19 — has a zoonotic source, meaning it's naturally transmissible from vertebrate animals to humans. And this is exactly why animals at the Oakland Zoo have begun getting inoculated against the disease it causes.

SARS-CoV-2 has proven to be highly transmittable across the animal kingdom. Domestic animals like dogs, cats, and rabbits have tested positive for COVID-19 over the past sixteen months; the same can be said about more exotic animals, including tigers, lions, and orangutans; animals belonging to both kinds of fauna classification have died from the disease, though symptoms appear to be milder than in humans.

In an effort to safeguard the Oakland Zoo’s resident animals (and on-site staff), keepers have started vaccinating the zoo’s big cats, bears, and ferrets against the coronavirus.

As reported by the Chronicle Saturday, the Oakland Zoo — an accredited zoological facility by the Association of Zoos and Aquariums (ASA) — is part of a national effort to protect animal species using an experimental vaccine.

"Up until now, we have been using public barriers at certain habitats to ensure social distancing, along with enhanced PPE worn by staff to protect our susceptible species from COVID-19," Alex Herman, vice president of veterinary services at the zoo, said in a released statement. "We’re happy and relieved to now be able to better protect our animals with this vaccine."

As of now, Herman noted that no animals at the zoo have tested positive for the disease.

In a tweeted video by the zoo, you can see staff members briefly poke a large male American black bear named Kern with a syringe; for the bear’s cooperation, he's then given a generous serving of whipped cream.

The vaccine doses were both developed and donated by Zoetis, a New Jersey-based research and development company that works to create certain veterinary medicines — which now includes formulating coronavirus vaccines for cats, dogs, poultry, and other animals.

Tigers Ginger and Molly — each of them forfeited over to the zoo after a private keeper in Texas realized the big cats were too dangerous to care for — were the first animals at the zoo to receive this round of Zoetis vaccines. (The zoo's great apes were given modified vaccines from Zoetics to help mitigate the chance of human-to-ape infections back in March.)

Much like with us humans, the inoculations must be administered in a two-stage series to be effective. The animals that were given vaccines will need another dose in a few weeks to have full immunity against COVID-19.

Soon, all of the zoo's primates and pigs will also be given the vaccines.

But Zoetis isn't just helping the East Bay zoological facility protect its animals against COVID-19. The veterinary pharmaceutical company is donating more than 11,000 doses for animals residing at nearly 70 zoos across the country in addition to a handful of rehabilitation centers, sanctuaries, and academic facilities.

Zoetis' efforts to safeguard animals against SARS-CoV-2 was a swift commitment after a dog became infected with the virus in Hong Kong back.

"When the first dog was infected with COVID-19 in Hong Kong last year, we immediately began to work on a vaccine that could be used in domestic animals," said Mahesh Kumar, senior vice president of global biologics at Zoetis, to KTVU. "More than ever before, the COVID-19 pandemic put a spotlight on the important connection between animal health and human health, and we continue to monitor for emerging infectious diseases that can impact animals as well as people."

The San Diego Zoo was the first AZA-accredited zoo in the country to start inoculating primates back in January after a COVID-19 breakout affected a troop of gorillas at its Safari Park.

Related: Oakland Zoo's Great Apes To Receive Modified COVID-19 Vaccines, Among the First in the World

Image: Justin Sullivan/Getty Images