Breakthrough cases get attention. But how many Idaho COVID cases are reinfections?

It’s not a simple question to answer. Here is why, and what public health officials do know.

By: - November 17, 2021 4:54 am
A microscopic image of human patient cells infected by the SARS-CoV2 virus.

This colorized scanning electron micrograph image shows a COVID-19 patient’s cell (green) heavily infected with SARS-CoV-2 virus particles (purple). (Courtesy of National Institute of Allergy and Infectious Diseases)

Idaho’s public health officials know the coronavirus managed to infect 17,099 fully vaccinated Idahoans since May 15.

They know 543 of those Idahoans with “breakthrough” cases were hospitalized, and 226 died.

How do they know? Public health analysts can cross-reference COVID-19 case records with immunization records and pinpoint when a person was “fully vaccinated” — two weeks out from their final dose of a COVID-19 vaccine — and the timeframe of their infection.

Health officials also know the virus infected 93,224 Idahoans who weren’t fully vaccinated since May 15. They know that 4,081 of those people were hospitalized, and 1,391 died — a much higher rate of serious illness and death compared with vaccinated Idahoans.

What they don’t know, and are trying to figure out, is how many of those unvaccinated Idahoans already had COVID-19 once or twice before.

Public health officials in the U.S. have begun to track and release data on reinfection rates. Pennsylvania just added more than 15,000 reinfections to its case totals, and Minnesota added about 7,600 reinfections.

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The state of Oklahoma went through a delta-fueled COVID-19 surge around the same time as Idaho. Their hospitals, too, became overwhelmed.

Oklahoma’s data show a 300% increase in reinfections during the delta surge. “While the number of reinfections is lower (than the number of vaccinated breakthrough cases), the rate of repeat cases is double the rate of breakthrough infections,” Public Radio Tulsa reported last month.

The known unknowns of COVID reinfections

Why doesn’t the Idaho Department of Health and Welfare publish a number of COVID-19 reinfections, like it does with post-vaccination breakthrough cases?

They’re working on it, officials say. But they don’t want to publish incomplete numbers. There are many hurdles in their way.

What do ‘reinfection’ and ‘breakthrough case’ mean, anyway?

Breakthrough case: When a person who is fully vaccinated gets infected with the coronavirus. “Fully vaccinated” means two weeks after completing the COVID-19 vaccine series.

Reinfection: The criteria laid out by the CDC are complex. But generally, these are considered to be cases of COVID-19 that occur more than 90 days after a person’s first infection.

Some of those hurdles apply to breakthrough cases and reinfections: Some people never know they’re infected, because they were asymptomatic, assumed they had allergies, couldn’t get a COVID-19 test, or took a home test which nobody reported to public health.

Some of the hurdles are unique to reinfections, though: Confirming a COVID-19 reinfection isn’t as simple as comparing the dates on a vaccine record and a laboratory test record. As contact tracing efforts have shown, some Idahoans are unwilling to participate in the public health process to limit the spread of COVID-19. There may never be a record of their first, second or subsequent infections.

This leaves a blind spot in what we know about Idaho’s COVID-19 situation.

That blind spot enables some — including Idahoans in positions of power like Lt. Gov. Janice McGeachin and Dr. Ryan Cole and others — to tout “natural immunity” for people who have already survived COVID-19. They can point to breakthrough cases more readily than reinfection numbers.

Meanwhile, a huge number of unvaccinated Idahoans who caught the delta variant in the past five months are now in a position to decide whether to vaccinate themselves or their COVID-recovered children, without having the full picture.

The U.S. Centers for Disease Control and Prevention recommends the vaccine for people who have recovered from a COVID-19 infection. And some research has suggested that the vaccine, plus post-infection immune response, may provide superior protection to COVID-19.

“We do have people who have been infected more than once in our data system,” said Idaho Deputy State Epidemiologist Dr. Kathryn Turner, in a Nov. 9 media briefing. “However, you can well imagine that there’s a lot of quality work that has to be done. So, we are working right now on going through all of the almost 300,000 cases and looking at those people who have been reported twice, sometimes three times, and making sure that the statistics that we can put out publicly are spot on. So that process is ongoing right now.”

Turner said in another recent media briefing that — because of the challenges in finding reinfections — her team was able to find 1% to 2% of people with a reported COVID-19 case this year, as of August, were previously infected, a similar rate to what’s been reported in Minnesota.

That would mean Idaho had a minimum of 750 to 1,500 cases of reinfection as of late August. If only 1% to 2% of the delta variant cases this fall were reinfections, that would add another 750 to 1,500 — for a total of at least 1,500 to 3,000. 

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What’s a better defense? Getting vaccinated or recovering from COVID-19?

Idaho public health experts and medical providers have told the public and the Idaho Capital Sun, with near-universal agreement: getting vaccinated is a better choice than taking your chances with the virus.

Their opinions are based on peer-reviewed studies, decades of experience in infectious disease, and what they know from other viruses and pandemics.

Their opinions also are based on the fact that obtaining “natural immunity” before vaccination means getting infected with the virus. While vaccines offer a controlled, limited introduction to what the coronavirus looks like, COVID-19 itself is unpredictable and uncontrollable.

As Idaho State Epidemiologist Dr. Christine Hahn said in a recent media briefing, health officials don’t want Idahoans to put themselves at risk by intentionally catching the virus.

Thousands of people have died from COVID-19 in Idaho, according to state records. More than 13,000 have been hospitalized. Untold numbers of Idahoans have long-term health issues because the virus invaded and destroyed cells in their body, or because their immune system was confused by the novel pathogen and wreaked havoc on their organs.

When it comes to reinfections, there is what’s known as a “survivorship bias” that clouds the data. Nobody who dies from COVID-19 will ever be reinfected. That takes 3,735 people out of the equation, in Idaho alone. Only about 6% of those deaths were among the vaccinated — typically, among people whose age and health likely kept them from developing adequate immunity. How many of the deaths were from a reinfection? We don’t know.

There are legitimate studies that show vaccines are superior at warding off COVID-19. There are legitimate studies that show “natural” infection can produce a robust immunity, too.

“But we have lots of studies and information from around the country and around the world about that,” Hahn said.

The CDC earlier this month published a large, multistate study that found hospitalizations for COVID-19 were 5.49 times more common among adults who previously had the disease three to six months earlier, than among adults who’d been fully vaccinated with Pfizer or Moderna shots three to six months earlier.

“The CDC has come out and said (people who recover from COVID-19 have) two months, three months, maybe six months of pretty good protection, but that vaccination is still recommended because there’s no way to know for sure who those folks are that are going to be protected and for how long,” Hahn said.

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Audrey Dutton
Audrey Dutton

Audrey Dutton, senior investigative reporter, joined the Idaho Capital Sun after 10 years at the Idaho Statesman. Her favorite topics to cover include health care, business, consumer protection issues and white collar crime. Dutton hails from Twin Falls. She attended college at Hamline University in St. Paul, Minnesota, and received a master's degree in journalism from Columbia University in New York City. Before coming home to Idaho, Dutton worked as a journalist in Minnesota, New York, Maryland and Washington, D.C. Dutton's work has earned dozens of state, regional and national awards for investigative reporting, health care and business reporting, radio journalism, data visualization and much more.

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