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After more than a year of the COVID-19 pandemic, most people are eager for life to return to normal, as it was before the pandemic.

But that time may never come.

COVID-19 likely “won’t go away,” said Dr. Peter Chin-Hong, an infectious disease expert at the University of California at San Francisco School of Medicine.

“Until vaccine equity is established, until people are not hesitant about the vaccine, this won’t go away,” he said.

Because COVID-19 was transmitted from animals to humans, and it’s unlikely that the world can vaccinate or euthanize all the animal carriers, the virus will continue to circulate, potentially indefinitely.

COVID-19 isn’t like other infectious diseases, such as smallpox, which was effectively eliminated after global vaccine efforts.

“It’s going to stay around and have flares,” Chin-Hong said.

“Unless we vaccinate everyone at the same time, you’ll have flares,” he said. “And every time you have a flare, there’s the possibility of creating variants.”

Some parts of the U.S. are effectively open, with very low viral case rates, such as in California, where Chin-Hong lives. But the physician doesn’t expect things to stay calm indefinitely.

He says the current low case rate in places like California is due to vaccination in combination with a huge spike in cases in the winter, during which people recovered and developed “natural immunity,” meaning immunity not from the vaccine, but from catching the virus.

Natural immunity likely fades faster than the protection from the vaccine — within 6 to 12 months, physicians believe. Once it fades in a majority of the population, that paves the way for “flares.”

Vaccine hesitancy is hardly an American-only problem. A recent Gallup poll found that nearly 1.3 billion adults would not agree to be vaccinated. Only two in three adults worldwide said they would get the vaccine – even if it was available to them at no cost – which isn’t enough for global herd immunity.

That said, Chin-Hong does believe life will return to “almost normal” eventually. He expects we’ll “feel relief regionally,” and develop regional herd immunity.

“There will probably be countries with much less disease than others,” he said. “But as long as we’re traveling back and forth, there’s potential for it to randomly flare up.”

Chin-Hong says measles provides a good example. A lot of people are immunized against it — but not everyone — and that means there will still be outbreaks occasionally when someone travels from elsewhere and exposes a large group of people not vaccinated against the disease.

The key is to get as many humans vaccinated against COVID as possible, and quickly, before new variants develop.

Ultimately, that’s the only avenue by which we can “squash COVID to the bare minimum,” Chin-Hong said.