The pattern certainly looks familiar.

COVID-19 cases are climbing again in much of Europe and Asia, including in China, where the largest surge since the virus first emerged from that country more than two years ago has resulted in several large factory cities being locked down.

But even though past COVID-19 outbreaks overseas soon spread to the United States and sent cases soaring, that doesn’t mean history will necessarily repeat itself, said Han Kim, a public health professor at Westminster College in Salt Lake City.

“It’s harder and harder to predict what’s going to happen here, given what’s happening in other places,” Kim said. “Different populations have different levels of immunity, different countries have different policies on lockdowns, vaccinations and so on.”

One of those policies, known as “zero COVID,” is not faring well, especially in China and Hong Kong, against the incredibly transmissible omicron variant of the virus that drove cases to record levels in Utah and the rest of the United States earlier this year.

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The trouble with attempting to shut out the virus altogether, Kim said, is that many people ended up never being exposed before omicron came along, so there was “essentially a huge population that’s immune naive” and vulnerable to infection, combined with less effective Chinese vaccines that some are refusing.

That’s led to the seven-day average of new cases in China increasing fivefold, to more than 1,500, according to The New York Times, causing lockdowns in several large factory cities that’s affecting the assembling of iPhones, as well as closures in Shanghai. In Hong Kong, nearly half of the population is thought to have been infected.

While omicron cases have already peaked in the United States, so-called “stealth omicron,” an even easier to spread subvariant, has yet to hit hard here.

More ‘stealth omicron’ found in Utah

The subvariant, known as BA.2 to scientists, is believed to be responsible for at least 50% of all cases in Europe, but now make up just over 23% of the cases in the United States and more than 13% in the region that includes Utah, according to the just updated latest estimate by the Centers for Disease Control and Prevention.

Since it first surfaced in Utah in January, 75 cases have now been identified among the COVID-19 test samples subjected to genome sequencing by the Utah Department of Health, said Kelly Oakeson, the state health department’s chief scientist for next generation sequencing and bioinformatics.

The number of omicron subvariant cases in Utah is expected to be updated by the end of the week

As of Feb. 27, the subvariant accounted for 3.7% of the sample of positive tests sequenced by the state, Oakeson said, compared to a CDC estimate of 4.7% for the region over the same time period. But the number of BA.2 cases sequenced continues to grow steadily, from seven cases in early February to 21 cases three weeks ago.

European countries, where often strict COVID-19 restrictions are being lifted and vaccination rates tend to be much higher than in the United States, are likely grappling with an increase in cases because of the spread of the subvariant, Kim said.

He said that’s a better explanation at this point than other theories, such as the suggestion that more cases are being detected in Europe because of waning immunity, or due to more frequent testing for the virus that includes easier access to home tests requiring results to be reported.

And Russia’s invasion of Ukraine, which has already forced nearly 3 million people, mostly women and children, to flee their homeland, may well end up adding to Europe’s case counts, Kim said, but so far, neighboring countries like Poland are not yet seeing the same spikes.

“As BA.2 increases here, will we see a surge similar to Europe?” Kim asked, adding he’s not so sure, even though some experts “think that by April, May, we’ll see that same surge as BA.2 starts to take over, and exceeds 50% of new cases.”

What about natural immunity from having the virus?

Unlike in Europe, where mitigation measures like mask mandates and vaccine requirements were largely followed, the professor said the milder but still extremely transmissible original omicron variant may have infected more people in the United States, providing some immunity against the subvariant.

Less than 62% of all Utahns are considered fully vaccinated against COVID-19, and just over 27% have also gotten a booster shot, considered key to preventing hospitalizations and death from omicron, which caused many breakthrough cases.

What’s not clear is how much natural immunity there is on top of vaccinations, Kim said.

“We really don’t have good data on that,” he said, due to what he termed “suboptimal” testing. At the height of the omicron surge, Gov. Spencer Cox urged most Utahns with symptoms to skip overwhelmed state testing sites and simply stay home. By the end of the month, private health care systems will largely take over testing.

Does omicron mean a new phase is coming for the COVID-19 pandemic?

Andy Slavitt, a former Obama administration official who served as a COVID-19 response adviser in the Biden administration, warned in a series of tweets Monday that, “an estimated 45% of the U.S. has had omicron recently. That should be highly protective.”

Slavitt said those who are vaccinated but haven’t had the omicron variant “should be vulnerable to infection from BA2, but largely won’t be hospitalized or worse. Those without prior infection would be at most risk of infection. Those who haven’t been infected but also aren’t vaccinated or boosted will be at highest risk of hospitalization.”

He predicted that based on European case increase, the United States “could see a new rise in COVID cases over the spring,” but those factors mean “we could see lots of cases, but an even lower portion” of people hospitalized than during the last wave.

Experts continue to stress the need for vaccinations and booster shots to protect against the most severe cases that can lead to hospitalization or even death from COVID-19, rather than relying on immunity from getting infected should there be another surge.

“By getting vaccinated, we could have reached the same level of immunity without all the deaths,” Kim said, citing the “preventable” loss among those who chose not to get the shots. “We reached this point, and people say, ‘See, this approach was the way to go.’ And in reality, no it wasn’t because how many people have died.”