It's being measured, not ignored.[1] This data is obtained by re-using random samples of blood drawn by commercial labs for other medical blood tests. In Vermont, under 3% of the population has had COVID-19. In Puerto Rico, about 49%. Huge variance by state. This does not include people immunized; the test used can differentiate.

[1] https://covid.cdc.gov/covid-data-tracker/#national-lab