Some vaccinated Utahns still contract COVID-19. Here’s what you need to know about these ‘breakthrough cases.’

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While they’re rare, there have been nearly 1,000 cases of COVID-19 confirmed in Utahns who are fully vaccinated, the Utah Department of Health says.

These so-called “breakthrough” cases are a tiny fraction of the overall number of people who have been vaccinated, and they carry with them a much smaller risk of hospitalization or death.

But as people who have been inoculated increasingly remove their masks in public spaces, health officials say it’s important they’re aware of the risk, however small, that they could still come down with the virus and spread it to vulnerable populations.

Many people who have received their shots think, “Oh, they’re 95% effective — it won’t happen to me,” noted Tom Hudachko, a spokesman for the Utah Department of Health. The reality is, though, that “some portion of individuals who get vaccinated are going to unfortunately become infected,” he said.

Here’s what you need to know about breakthrough cases of COVID-19:

How many people in Utah have gotten COVID-19 after vaccination?

As of mid-week last week, public health officials had documented 993 COVID-19 cases affecting people who are fully vaccinated, according to the Utah Department of Health.

Compared to the 1.3 million people that the state coronavirus dashboard now shows have now been fully vaccinated, the risk of getting COVID-19 following vaccination is incredibly low. And those who do get COVID after they’ve been inoculated are less likely to be hospitalized or to die from the disease.

This data shows that “the vaccines are tremendously effective,” Hudachko said.

Because they’re vaccinated, and since their symptoms tend to be more mild, it’s possible that some immunized people who have breakthrough cases might be less likely to think about getting tested.

The real number of Utahns who have had breakthrough cases is probably higher than health department data shows, Hudachko acknowledged, since their data is “representative of people who go and get tested.”

“There are certainly fully vaccinated people out there who have not gone and gotten tested who may have been infected,” he added. “So it likely is underrepresented, but that’s true of just our general case count as well. The degree to which it’s underrepresented would be really hard to determine.”

Why do some people get COVID, even though they’re fully vaccinated?

All three of the vaccines currently in circulation in the United States are highly effective at protecting the people who receive them from contracting COVID-19.

But “no vaccine is 100% effective,” Hudachko noted.

The Pfizer vaccine is 95% effective at preventing cases of COVID-19, while Moderna was 94.1% in clinical trials, the Centers for Disease Control and Prevention (CDC) has reported. The single-dose Johnson & Johnson vaccine was found to be 66.3% effective in clinical trials and since then, 72% in the U.S.

These numbers mean that some portion of the population, despite being vaccinated, is likely to contract COVID-19.

The shots are largely effective against more contagious virus variants that continue to circulate chiefly among people who are unvaccinated, state health officials note. But the CDC notes that the presence of these mutations make it more likely that someone will experience a breakthrough case.

In Utah, Hudachko said variants are primarily affecting people who are unvaccinated, with around 97% of cases over the past two months among unvaccinated people.

“What’s happening is that the variants and original COVID are spreading in unvaccinated populations,” he said. “So that’s where the concern is right now.”

Do we know which variants are involved in these breakthrough infections?

The state health department tries to “sequence” the cases of vaccinated people who have tested positive for COVID-19, so they can identify which variant infected them.

Health officials aren’t able to do this with every test sample — rapid antigen tests aren’t eligible for sequencing — so we don’t have a full picture of which variants are breaking through.

But of the 203 breakthrough cases that public officials had tried to sequence as of last week, there were 93 cases of the U.K. or Alpha variant, which the CDC said earlier this month is now the dominant strain of COVID-19 in the United States.

Four cases were of the South Africa or Beta variant; 20 were of the California or Epsilon variant, two were of the India or Delta variant and two were of the Brazil or Gamma variant. Another 42 were from “other lineages” and 40 could not be sequenced, according to the Health Department.

Tara Scribellito, an infectious disease nursing supervisor at the Salt Lake County Health Department, said the agency is monitoring COVID-19 breakthrough cases within its jurisdiction to determine trends among variants and to see if there’s one that’s commonly escaping the protection of the vaccines.

“It’s a good thing to monitor so we know what’s going on in the community and we can respond appropriately,” she said.

Are some people more prone to breakthrough cases than others?

Older adults may be more likely to develop breakthrough infections due to weaker immune responses to the vaccines, as could people who are immunocompromised, The New York Times has reported.

The CDC is gathering data to identify whether there are any trends among people who have gotten breakthrough cases, whether it be age, sex, underlying health conditions or the type of vaccine. So far, “no unusual patterns have been detected.”

Hudachko said he didn’t have immediate information on trends in breakthrough cases in Utah, including data on which vaccine each of the inoculated people received.

Scribellito said her research into the subject hasn’t found a significant difference in cases among vaccinated people based on which vaccine someone got or based on their age.

“We have had vaccine breakthrough cases reported to us from age 16 all the way to in the 90s,” she noted. “We haven’t really seen any major trends so far.”

Do people who get COVID-19 after they’ve been vaccinated get as sick as people who aren’t?

There is “some evidence” that people who get COVID-19 after the vaccine may face less severe symptoms, the CDC notes.

The data in Utah indicates that people who have contracted the coronavirus after vaccination are much less likely to be hospitalized than those who haven’t received their shots. Of the 993 people who have been fully vaccinated and contracted breakthrough cases, 106 were hospitalized. And just three died.

“The vaccine remains the absolute best way to protect yourself from not only getting COVID-19 but from getting a severe enough case that it requires hospitalizations or causes death,” Hudachko said.

How concerned should we be about breakthrough cases?

Because the percentage of vaccinated people who have gotten COVID-19 is so minuscule, Scribellito said she “wouldn’t worry about the vaccine breakthrough cases.”

“Even if someone does end up being a vaccine breakthrough case, generally it’s a much more mild version of COVID than you risk by not getting vaccinated at all,” she noted.

Public health officials recognize the breakthrough cases as an inevitability, added Hudachko. And since the numbers of cases have been in line with expectations, he said the numbers in Utah aren’t a cause for much concern and should actually be cause for celebration.

“We’re really encouraged by the numbers that we’re seeing,” he said. “The vaccine works and it works very well.”

Is there anything else people who are fully vaccinated should know about breakthrough cases?

While attention has turned away from coronavirus testing in the past few months, public health officials are still encouraging anyone who develops symptoms of the virus to get tested — even if they’re fully vaccinated.

That way, they’ll know to isolate if they’re positive, to avoid spreading the virus to vulnerable people who are immunocompromised, can’t get vaccinated for a variety of reasons or have a poor immune system.

“Testing is still a really important part of containing the outbreak,” Hudachko said. “If we don’t know who is positive, we can’t get those people information about isolation and we can’t get people around them information about quarantine.”