The ADEA is a federal law which prohibits employment discrimination against individuals age 40 and older. For example, the ADEA would prohibit an employer from intentionally excluding an individual from the workplace based on his being 65 years or older. This prohibition would hold true even if the employer acted for altruistic reasons, such as protecting the employee due to a higher risk of severe illness from COVID-19.
Unlike the ADA, the ADEA does not include the right to reasonable accommodation due to age. However, it should be noted that employers are free to provide additional flexibility to workers age 65 and older due to their increased risk. This is not barred by the ADEA, even if younger workers are treated less favorably based on age in comparison.