Adults 20 to 49 may have caused 72% of COVID-19 outbreaks in the United States

Adults aged 20 to 49 may have triggered 72.2% of COVID-19 resurgences in the United States as of late summer 2020, with those 35 to 49 making a particular contribution, a study published yesterday in Science suggests.

A team led by researchers at Imperial College London analyzed age-specific cellphone mobility data from more than 10 million Americans and linked it to COVID-19 death data specific to the age from March 15, 2020.

Data from 42 US states, Washington DC and New York showed that the number of visits to places such as supermarkets and restaurants began to rebound across all age groups in August after an initial reduction significant due to public health interventions such as lockouts. in spring. COVID-19 infections and deaths have followed a similar pattern in the United States and Europe.

Among all sites assessed, up to mid-August, the 35-49 age group reportedly contributed 41.1% of virus transmission, compared to 2.1% among 0-9 and 4 , 0% among 10 to 19, 34.7% among 20 to 34, 15.3% among 50 to 64, 2.5% among 65 to 79 and 0.3% among 80 and more. The number of coronavirus deaths did not increase significantly after schools reopened in the fall.

The proportion of different age groups among deaths from COVID-19 has remained relatively constant over time, in contrast to large changes in their relative proportion of cases.

“Based on the combined mobility and mortality data, we find that the reconstructed fluctuations in breeding numbers by age had only a relatively small impact on the age group contribution to the spread over time. , and no evidence that young adults between the ages of 20 and 34 were the primary source of the COVID-19 resurgence in the United States in the summer of 2020, ”the authors wrote.

But in October 2020, the 20 to 49 age group was the only one to have a reproduction number – or number of secondary people infected per case – greater than 1, which is the level needed for an epidemic to spread. . The estimated contribution to the spread by age group at that time was 72.2% for adults aged 20-49, compared with less than 5% for children aged 0-9 and less than 10% for adolescents aged 10 to 19.

Targeted interventions to stem the spread, deaths

Over time, COVID-19 transmission rates varied widely across the United States, with higher rates attributed to the 20-49 age group and those aged 20-34 in the regions. from the south, southwest and west of the country.

“We are finding that adults between the ages of 20 and 49 are a major driver of the COVID-19 epidemic in the United States and are the only age groups disproportionately contributing to the spread, compared to the size of their population, ”said lead author Melodie Monod, MSc. a press release from Imperial College London. “As children and adolescents contribute more to the spread of COVID19 since the school closure warrants were lifted in fall 2020, we see that this dynamic has not changed much since the school reopened. .

The authors called for targeting interventions such as vaccines reducing transmission in people aged 20 to 49 as a strategy to reduce the likelihood of future outbreaks of COVID-19 and associated deaths in areas not yet affected by new highly transmissible coronavirus variants. “Adults aged 20 to 49 naturally have most contact with other adults aged 20 and older,” the authors wrote in the study, adding that the age group is both more vulnerable. virus and more mobile than young people.