According to the Center for Disease Control and Prevention, "In the United States, most available vaccine effectiveness data are related to mRNA vaccines (Pfizer-BioNTech and Moderna) because these vaccines have been available longer and are used more widely."
You can visit the Morbidity and Mortality Weekly Report (MMR) on the Center for Disease Control and Prevention website every week. A report released on August 13, 2021 included the data table below. It shows the number of cases by age group under the age of 65 years old.
From the COVID-19 Vaccine Effectiveness, Center for Disease Control and Prevention, https://www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/how-they-work.html