Over the past year, coronavirus vaccines have reached billions of human arms, and the fuzzy haunches of an ark of zoo animals. jaguars they are getting the jab. The bonobos are being dosed. So are orangutans and otters, ferrets and fruit bats, and of course lions, tigers, and bears (oh my!).
Largely left behind, however, are two creatures much closer to home: domestic cats and dogs.
Pet owners have taken notice.
“I get so many questions on this topic,” said Dr. Elizabeth Lennon, a veterinarian at the University of Pennsylvania. “Will there be a vaccine? When will there be a vaccine?
Technically, a pet vaccine is feasible. In fact, several research teams say they have already developed promising vaccines for cats or dogs; the vaccines that zoo animals receive were initially designed to dogs.
But vaccinating pets is simply not a priority, experts said. Although dogs and cats can catch the virus, there is growing evidence to suggest that Fluffy and Fido play little or no role in its spread, rarely getting sick.
“I think a vaccine is pretty unlikely for dogs and cats,” said Dr. Will Sander, a veterinarian at the University of Illinois Urbana-Champaign. “The risk of disease and illness spreading in pets is so low that it would not be worth giving any vaccine.”
A positive Pomeranian
In February 2020, a woman in Hong Kong was diagnosed with Covid-19. Two other people in her home soon tested positive for the virus, as did an unexpected family member: a old pomeranian. The 17-year-old dog was the first known pet to contract the virus.
But not the last. A German shepherd in Hong Kong soon tested positive as well, as did the cats in Hong Kong, Belgium and New York. The cases were extremely mild: the animals had few or no symptoms, and experts concluded that humans had transmitted the virus to pets, and not the other way around.
“To date, there have been no documented cases of dogs or cats transmitting the virus to people,” Dr. Lennon said.
But the prospect of a pet pandemic sparked interest in an animal vaccine. Zoetis, a New Jersey-based veterinary pharmaceutical company, started working on one as soon as they learned of the Hong Kong Pomeranian.
“We thought, ‘Wow, this could get serious, so let’s start working on a product,’” said Mahesh Kumar, a Zoetis senior vice president who leads vaccine development.
As of fall 2020, Zoetis had four promising vaccine candidates, each causing “robust” antibody responses in cats and dogs, the company announced. (The studies, which were small, have not been published.)
But as vaccine development progressed, it became increasingly clear that infection from pets was unlikely to pose a serious threat to animals or people.
On a study of 76 pets living with people who had the virus, 17.6 percent of cats and 1.7 percent of dogs also tested positive. (Studies have consistently shown that cats are more susceptible to infection than dogs, perhaps for biological and behavioral reasons). Of the infected pets, 82.4 percent had no symptoms.