The US-Norwegian team noted that because COVID-19 severity is generally lower among children, the overall burden from this disease is expected to decline as the SARS-CoV-2 virus becomes endemic in the global population.
“The following infection by SARS-CoV-2, there has been a clear sign of increasingly severe outcomes and fatality with age,” said Ottar Bjornstad from the University of Oslo in Norway.
“Yet, our modelling results suggest that the risk of infection will likely shift to younger children as the adult community becomes immune either through vaccination or exposure to the virus,” he said.
The study, published in the journal Science Advances, noted that such shifts have been observed in other coronaviruses and influenza viruses as they have emerged and then become endemic.
“Historical records of respiratory diseases indicate that age-incidence patterns during virgin epidemics can be very different from endemic circulation,” Bjornstad said.
“For example, ongoing genomic work suggests that the 1889-1890 pandemic, sometimes known as the Asiatic or Russian flu — which killed one million people, primarily adults over age 70 — may have been caused by the emergence of HCoV-OC43 virus, which is now an endemic, mild, repeat-infecting cold virus affecting mostly children ages 7-12 months old,” he said.
Bjornstad, however, cautioned that if an immunity to reinfection by SARS-CoV-2 wanes among adults, the disease burden could remain high in that group, although previous exposure to the virus would lessen the severity of the disease.
The researchers analysed disease burden over immediate, medium, and long terms — 1, 10, and 20 years, respectively.
They also examined disease burden for 11 different countries — China, Japan, South Korea, Spain, UK, France, Germany, Italy, the US, Brazil, and South Africa — that differed widely in their demographics.