Study Results Suggest SARS-CoV-2 Could Become Mild, Seasonal Virus

The results of a study published in Viruses suggests that SARS-CoV-2 could become a mild, seasonal illness not unlike the common cold over the course of the next decade.

The investigators used mathematical models that incorporate lessons learned from the pandemic on how the body's immunity changes over time to predict the potential course of COVID-19.

“This shows a possible future that has not yet been fully addressed,” Fred Adler, PhD, professor of mathematics and biological sciences at the University of Utah in Salt Lake City, said in a statement. “Over the next decade, the severity of COVID-19 may decrease as populations collectively develop immunity.”

The study results suggest that changes in the disease could be driven by changes in the human immune response to SARS-CoV-2, as opposed to any changes in the virus itself. Other seasonal coronaviruses circulate in the human population that are far more benign.

Some evidence indicates that one of these viruses might have once been more severe, giving rise to the Russian flu pandemic in the late 19th century, according to the study authors.

To test whether the severity of SARS-CoV-2 could similarly lessen over time, the investigators built mathematical models incorporating evidence on the body's immune response to SARS-CoV-2 based on data from this pandemic. Points of consideration included the likelihood that adults who have had COVID-19 or have been vaccinated are protected against severe disease, children are unlikely to develop severe disease, and larger doses of the virus cause greater viral shedding and more severe disease. Running several versions of these scenarios showed that these 3 mechanisms in combination could potentially result in a situation where an increasing proportion of the population becomes predisposed to mild disease over the long term.

The models demonstrate that as more adults become partially immune, whether through prior infection or vaccination, severe infections all but disappear over the next decade.

The investigators said that, eventually, only children will be exposed to the virus for the first time, and children are naturally less prone to severe disease.

The models do not account for the possibility that new virus variants overcome partial immunity. Additionally, the predictions rely on these central 3 assumptions remaining static.

“Our next step is comparing our model predictions with the most current disease data to assess which way the pandemic is going as it is happening,” Adler said.

“Do things look like they're heading in a bad or good direction? Is the proportion of mild cases increasing?” Adler asked.

“Knowing that might affect decisions we make as a society,” he said.

Reference

Will COVID-19 eventually become just a seasonal nuisance? News release. EurekAlert. May 20, 2021. Accessed May 21, 2021. https://eurekalert.org/pub_releases/2021-05/uouh-wce052021.php