Updated October 8, 2021 - 6:21 pm
The Nevada State Public Health Laboratory has identified a rare case of COVID-19 reinfection occurring just 22 days after the patient first tested positive.
The patient, an unvaccinated 31-year-old Mineral County man with no underlying health conditions, first tested positive for the delta variant and then, three weeks later, for a different strain that evolved from the delta variant, Mark Pandori, director of the lab at the University of Nevada, Reno’s School of Medicine, told the Review-Journal this week.
Infection from COVID-19 typically results in immunity from reinfection for a minimum of several months, according to the Centers for Disease Control and Prevention. Such rapid reinfection, especially in a young and healthy individual, could mean that the virus has mutated to a degree that makes it more resistant than previously seen to the protection afforded by past infection or from vaccination.
More such reinfections would first need to be identified to know if this is the case.
“We don’t know how widespread the phenomenon is right now, but it implies that the virus is definitely going to be fine in terms of staying in circulation in the population,” given how much the strain that caused the reinfection differs from the delta variant, he said.
The strain, a sublineage of delta known as AY.26, has 31 genetic differences from delta, including on the spike protein, the part of the virus targeted by vaccines, he said. It is this genetic variety that especially concerns him.
“My concern is that there’s a scientific rationale for this being indicative of a bigger problem,” said Pandori, whose lab in August 2020 reported the first known case of COVID-19 reinfection in North America.
That bigger problem is the possibility of increasing numbers of reinfections as well as so-called breakthrough cases in vaccinated individuals.
The Centers for Disease Control and Prevention did not respond to a request for comment other than to state that the request had been received.
Health officials have said that they expect that COVID-19 vaccines ultimately will have to be adjusted to protect against new strains of COVID-19, much as flu vaccines are recalibrated each year.
“If there were variants that could evade the protection, in some notable way, of our vaccines, and could spread reasonably fast — and if it were also reasonably contagious — then we would have to quickly create a specific vaccine against that variant,” said Dr. William Schaffner, a professor in the infectious disease division at Vanderbilt University.
However, at this point, health authorities stress that the current vaccines continue to protect against serious illness from the coronavirus.
Delta variants are rising
The Mineral County man who became reinfected did not require hospitalization and has recovered, said Christina Boyles, deputy health officer for the rural Nevada county, which has a population of about 4,500.
It was Boyles who first spotted the usual case.
“I speak with just about every single positive case that comes through Mineral County,” which has reported close to 700 cases since the beginning of the pandemic, she said. That figure includes cases in members of the Walker River Paiute Tribe.
What caught her attention was that the individual, after having tested positive on Aug. 16 and recovering, again tested positive on Sept. 7 using a rapid test, which typically picks up only high viral loads and active infections. The results were confirmed through a more sensitive PCR test. The man’s symptoms were more severe the second time around.
The state lab then compared genetic samples from the tests in August and September, determining that they were different strains and separate infections.
The state lab, which genetically analyzes or sequences a sampling of positive COVID-19 test results, has identified approximately 300 cases of AY.26 across the state, including in Southern Nevada, Pandori said.
The sublineages that have mutated from delta are becoming more prevalent. A report this week by the state lab shows that the delta variant remains the dominant strain in Nevada, accounting for 63 percent of the cases genetically analyzed in the past 30 days. Rounding out the top 5 most prevalent lineages are four mutants of delta — AY.4, AY.25, AY3 and AY13 — accounting for 29 percent of genetically sequenced cases.
“These sublineages — there’s more than just AY.26 —are really taking over,” he said. “The original delta variant is sort of descending rapidly in terms of its prevalence and giving way to its sublineages.
“And to me, this is going to be how the virus stays in the population until winter, when it’s probably gonna have a lot more of an opportunity to spread.”