Most COVID-19 spread by younger adults, early middle-agers
The vast majority of new COVID-19 infections trace to COVID-positive adults between the ages of 20 and 49, according to a new study published in Science.
That age group has sustained a resurgence in transmission of the virus since October 2020, accounting for at least 65 of 100 infections. The finding suggests targeting this age demographic for transmission-blocking vaccines could be a critical part of sound public health strategy.
Researchers analyzed data and trends from more than 10 million people in the U.S. and linked it to age-specific COVID-19 mortality data. The investigation showed contact patterns ebbed and flowed over the course of the pandemic in 2020, with the average number of daily contacts made by a single individual dropping in late March when stay-at-home orders were first issued around the U.S.
The study team tracked mobility trends using a national-level, aggregate mobility dataset of cell phone data. From this they were able to pinpoint mobile device signal locations of user visits to shops, parks and universities.
“During the initial phase of epidemic spread, trends declined most strongly among individuals aged 18-24 years across almost all states and metropolitan areas, and subsequently tended to increase most strongly among individuals aged 18-24 in the majority of states and metropolitan areas, consistent with re-opening policies for restaurants, night clubs and other venues,” wrote first author Melodie Monod, of the Department of Mathematics at Imperial College London, et al.
The authors noted that cell phone signals are hard to analyze due to fluctuations in location data. The data was incorporated into a Bayesian contact-and-infection model describing contact and transmission dynamics at the state- and metropolitan area-level across the U.S.
In particular, adults aged 35 to 49 have been driving the resurgent COVID-19 epidemics in the U.S. Adults in the age group 20 to 49 accounted for about 72% of COVID-19 infections in the U.S. after school reopenings in October 2020, compared to less than 5% originating from children 0-9 and less than 10% from teens aged 10 to 19.
“Over time, the share of age groups among reported deaths has been remarkably constant, suggesting that young adults are unlikely to have been the primary source of resurgent epidemics since summer 2020, and that instead changes in mobility and behavior among the broader group of adults aged 20-49 underlie resurgent COVID-19 in the U.S. in 2020,” the authors wrote.
Amy joined TriMed Media as a Senior Writer for HealthExec after covering home care for three years. When not writing about all things healthcare, she fulfills her lifelong dream of becoming a pirate by sailing in regattas and enjoying rum. Fun fact: she sailed 333 miles across Lake Michigan in the Chicago Yacht Club "Race to Mackinac."