Jennifer Spittler had errands to run on the second Friday in August, but first she had to run herself – so it is when you’re training for a half marathon. Speed work was the order of the morning. She noticed she was having a harder time catching her breath between intervals than normal. The 38-year-old occupational therapist figured it must be the wildfire smoke hanging in the Denver air.

She got on with her day, stopping by Target and the car wash with son Luke, 5. But she still wasn’t quite herself. She felt, as he put it, “kid of foggy-headed and off,” and by that evening, she knew she was coming down with something.

She took a COVID-19 test the next morning. It came back positive.

This was a coronavirus breakthrough infection. The health care worker had received her second shot in early January. She had dodged the coronavirus long before that: her husband Jack, a physician at UCHealth A.F. Williams Family Medicine Clinic – Central Park, had tested positive for COVID-19 in March 2020. But neither Jennifer nor Luke nor Luke’s brother Josh, 2, had been infected.

“I did feel a little bit invincible,” she said.

Breakthrough COVID-19 infection

Spittler quarantined from work for 10 days, wore a mask at home, and skipped family meals. Her sense of taste disappeared four or five days after that morning run, then slowly crept back. She continued to feel under the weather, using her albuterol inhaler for shortness of breath and taking afternoon naps to clear the fog and fatigue. But within a week she tried her luck on a stationary bicycle and, a couple of days after that, was out running again. The boys and Jack tested negative.

Spittler’s case was both uncommon and typical. Breakthrough infections among the vaccinated happen, but when they happen, particularly among the young and otherwise healthy, you may get sick, but you probably won’t get terribly sick. That said, “We’re seeing breakthrough in some patients, and we’re also seeing it with our providers here,” said Dr. Corey Lyon, a CU School of Medicine physician and medical director of UCHealth A.F. Williams Family Medicine Clinic – Central Park.

Dr. Wagner Schorr-Ratzlaff, a University of Colorado School of Medicine and UCHealth physician at UCHealth Internal Medicine – Lowry, said they’re seeing breakthrough cases too. In mid-August, he had a virtual visit with an 83-year-old patient who had a 102-degree fever, cough, and shortness of breath. The patient ended up in the ICU. His wife 81, had sniffles and minor symptoms. Both had been vaccinated; both tested positive for COVID-19. The previous week, Schorr-Ratzlaff had seen breakthrough infections with two patents in their 30s and 40s who had minor symptoms, and with a 61-year-old whose illness fell somewhere between the above.

“It’s really just been in recent weeks that we’ve been seeing these breakthrough infections,” Schorr-Ratzlaff said.

It’s the variant

Waning vaccine-induced immunity may play a role, but the main issue is the delta variant. It’s more than twice as transmissible as the initial coronavirus, and it now comprises more than 99% of cases in Colorado. The variant appears to be twice as likely to put you in the hospital as the alpha (British) variant that was dominant before it. The U.S. Centers for Disease Control and Prevention (CDC) says the vaccinated can transmit it without knowing they have it (though the prevalence of asymptomatic breakthrough infections remains unclear for now).

Delta has led physicians such as Lyon and Schorr-Ratzlaff to mask up again when they’re grocery shopping and elsewhere indoors where people congregate. But both will tell you – and the data back them up – that breakthrough infections are far less of a problem than infections among the unvaccinated.

A CDC study found that the unvaccinated were five times more likely to contract COVID-19 and 29 times more likely to be hospitalized. While case numbers went up with the delta variant’s emergence, those ratios held firm even as it took over.

Of the 171 million in the United States who had been vaccinated as of Aug. 23, there had been 6,782 non-fatal hospitalizations and 1,623 deaths directly related to COVID-19. If you’re vaccinated, that translates into a roughly one-in-25,000 chance of hospitalization and a one-in-105,000 chance of death. Further, if you’re under 65, the odds bad outcomes are slimmer yet, because 70% of the hospitalizations and 87% of the deaths were among those older than that.

As of Sept. 16, 87% of those 65 and older in Colorado had been fully vaccinated, and 92% had had at least one shot. But the younger cohorts have not kept pace: 69% of those eligible in Colorado (those ages 12 and older) had been vaccinated and 76% had had at least one dose. Kids under 12 are still waiting for U.S. Food and Drug Administration emergency approval of a coronavirus vaccine.

Vaccination is key

The robust antibody response from third shots for the immunocompromised and boosters for the previously vaccinated should stop many breakthrough infections. But they’ll still happen. For now, Schorr-Ratzlaff, Lyon, and their colleagues are focusing on those at the greatest risk of coronavirus infection by educating the unvaccinated on the good the vaccine can do them and those around them. Lyon estimates that the unvaccinated account for more than 90% of the COVID-19 infections coming through AF Williams.

He talks to patients about the safety and efficacy of the vaccines, then brings up the importance of protecting not only themselves, but also their neighbors. If there is still reticence, Lyon has them reflect on what their live were like over the past year – the restrictions, the mandates, the isolation.

“Don’t you want to go back to life being normal again?” he asks. “This is the way we can get there.”

Schorr-Ratzlaff checks for unvaccinated patients on his schedule each morning.

“I’m sitting down and talking very seriously with everyone who’s unvaccinated,” he said.

Both AF Williams and UCHealth Internal Medicine – Lowry the Johnson & Johnson vaccine onsite. (For Pfizer and Moderna vaccines, which must be stored in an ultracold freezer, physicians refer patients to UCHealth University of Colorado Hospital on the Anschutz Medical Campus).

Two weeks after her breakthrough infection, Jennifer Spittler was back at work – and back to half-marathon training. Her sense of taste and smell remain works in progress, but otherwise she’s back to normal.

“I don’t’ feel like I can complain too much, because it was fairly mild,” she said. “But I wasn’t working, I wasn’t able to do much with my kids, and they still had to quarantine with me. I wouldn’t want to do it again.”

Also, Spittler knows her coronavirus infection could have been much worse.

“Who knows what it could have been without the vaccine?” she said.