Are Researchers Closer to Understanding Who is at Risk of Hospitalization From COVID-19?

Hospital patient

Amid new hope that the worst of the pandemic is in the past, the United States has rolled out a bivalent – half original strain and half Omicron BA.4 and BA.5 – COVID-19 booster, available to those 6 months and older. Tools like vaccines, antivirals, masking, improved ventilation and other measures help minimize infections. But what lessons have researchers learned about what makes someone more vulnerable to more severe COVID-19 if they become infected, and how can this improve care for patients with the disease?

Some answers may be found in a study published in The Lancet’s eBioMedicine that offers some important insights into characteristics that are linked with more severe COVID cases, as well as those suffering from post-acute sequelae of COVID-19, commonly termed “long COVID.”

In contrast with smaller and shorter-duration studies that preceded it, the current multi-center study from Drexel researchers and colleagues nationwide, enrolled 1,164 adult symptomatic patients from 20 U.S. hospitals from May 5, 2020 through March 19, 2021 as part of the “Immunophenotyping Assessment in a COVID-19 Cohort” (IMPACC) study. The researchers studied the severity of patients’ disease, time they spent in the hospital, viral load and other markers, at three-month intervals up to one year after they left the hospital.

Results showed being over the age of 65, of Latinx ethnicity, experiencing chronic diseases alongside COVID-19, presence of lung infections, higher levels of virus in the body and other biomarkers were linked to more severe COVID-19 and worse outcomes. Although female sex was associated with greater risk of long-COVID symptoms, male sex was associated with greater likelihood of being hospitalized for COVID-19.

Moreover, patients in the study who died from COVID-19 were slower to eliminate the virus from their body and showed the lowest levels of antibodies known as anti-RBD and anti-S IgG. As less ability to clear the virus may be a factor in fatal cases of the disease, the team created a novel calculated ratio (IgG/Ct value) to help medical teams assess whether a patient may be at greater risk of severe symptoms or death from COVID.

“Given the viral load findings, we now have a way to identify those at highest risk for death and complications by using the PCR cycle threshold,” said study co-author Charles Cairns, MD, the Walter H. and Leonore Annenberg Dean, and senior vice president of medical affairs at Drexel University’s College of Medicine. “Ironically, it is a measurement that has always been available to hospital laboratories using COVID-19 PCR tests, but has not been reported out to clinicians, much less used for decision-making.”

Although the study took place before the Delta and Omicron variants, Cairns says the findings from this work may help put the field closer to a possible explanation behind the different clinical courses that COVID-19 patients take. 

“Clearly, something is effecting those with higher viral counts, including evidence that their immune system is not responding the same as those with lower counts,” said Cairns. “Plus, this has implications for vaccination and boosting – keeping your antibodies counts high could help keep viral counts remain low if you become infected.”

The study, “Phenotypes of Disease Severity in a Cohort of Hospitalized COVID-19 Patient: Results From the IMPACC Study,” is available here. The study was funded by the National Institute of Allergy and Infectious Disease (NIAID).

Media interested in talking to Cairns should contact Greg Richter, assistant director, News and Media Relations, at or 215.895.2614.

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