From [HERE] A new CDC study shows that the record number of infections during the Omicron wave gave many Americans infection-induced immunity. Between December 2021 and February 2022, the estimated percentage of the U.S. population with infection-induced antibodies increased from 34% to 58% across all age groups. The largest increases were in children and adolescents (see figure below).

Here are the details from the CDC report:

During December 2021–February 2022, overall U.S. seroprevalence increased from 33.5% (95% CI = 33.1–34.0) to 57.7% (95% CI = 57.1–58.3). 

Over the same period, seroprevalence increased from 44.2% (95% CI = 42.8–45.8) to 75.2% (95% CI = 73.6–76.8) among children aged 0–11 years and from 45.6% (95% CI = 44.4–46.9) to 74.2% (95% CI = 72.8–75.5) among persons aged 12–17 years. [Note the very high levels reached for children.]

Seroprevalence increased from 36.5% (95% CI = 35.7–37.4) to 63.7% (95% CI = 62.5–64.8) among adults aged 18–49 years, 28.8% (95% CI = 27.9–29.8) to 49.8% (95% CI = 48.5–51.3) among those aged 50–64 years, and from 19.1% (95% CI = 18.4–19.8) to 33.2% (95% CI = 32.2–34.3) among those aged ≥65 years.

Look at the figure below to more clearly see how the natural immunity increased for different age groups. [MORE]