There are likely several reasons for the increase, according to the paper’s authors, who are researchers at the National Cancer Institute in Rockville, Maryland.

The overall distribution of the disease shifted toward younger people in the second year of the pandemic, both because high mortality rates had already reduced the older population, and since vaccination campaigns started with the most vulnerable, relatively younger people remained more exposed to severe cases of covid for a longer period of time.

While the Centers of Disease Control and Prevention’s data tracks vaccine uptake in different age brackets than the study—30 to 49 and 50 to 64—the breakdown can also offer an indication about vaccine uptake in the 45-54 cohort, as vaccine hesitancy is relatively high among both groups: 37% of all unvaccinated people are between 30 and 49, compared to 32% of all vaccinated people, and 26% of unvaccinated people are between 50 and 64, compared to 24% of all vaccinated people. The low vaccine uptake, combined with relaxed containment measures for covid (such as social distancing, masking), may have led to the increase in deaths.

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