TORONTO -- Cats could play an important role in the search for a coronavirus vaccine, according to new research that builds on our current understanding of how COVID-19 affects pets.

The new research, published Tuesday by the Proceedings of the National Academy of Sciences, studied seven cats and three dogs that were injected with the virus and studied by researchers at Colorado State University.

Researchers found that, while cats can infect other cats through direct contact, the dogs did not spread the virus amongst each other. Neither the cats nor dogs actually developed clinical symptoms of the COVID-19 at any point in the study.

“We report that cats are highly susceptible to infection, with a prolonged period of oral and nasal viral shedding that is not accompanied by clinical signs, and are capable of direct contact transmission to other cats,” researchers wrote in their findings.

“Resistance to reinfection holds promise that a vaccine strategy may protect cats and, by extension, humans.”

Because cats can spread the virus to each other and have a natural immune response to the virus, researchers say they may be useful in helping test vaccine candidates. At least nine vaccine candidates are in stage three of testing, the final step involved in determining if a vaccine is able to stop the virus from infecting the body.

“Perhaps most importantly, cats develop significant neutralizing antibody titers and are resistant to reinfection, although the duration of immunity is not currently known. This could prove a useful measurement for subsequent vaccine trials for both human and animal vaccine candidates,” researchers wrote.

There is no evidence to suggest that dogs or cats spread the virus to humans. Minks are the only animals believed to be able to pass the virus directly to humans after a series of outbreaks at mink farms in Europe. However, it is possible for humans to pass along the virus to animals in a process known as “reverse zoonosis.”

The new findings bolster Canada’s current guidelines on pets, which suggest that cats can infect cats but dogs can’t infect other dogs.

The research also bolsters calls from public health authorities to avoid all contact with pets if you become infected with COVID-19. 

“Infected pet cats should not be allowed to roam freely outdoors to prevent potential risk of spreading infection to other outdoor cats or wildlife,” researchers wrote. 

Previous research suggested that cats have a strong natural immune response to the virus and can spread the infection from on animal to another.