According to a release by the Centers for Disease Control and Prevention, 140 million U.S. residents or 43 percent of the population have been exposed to COVID.  The data was based on blood tests examined in commercial laboratories and from blood donations.  The survey period extended to January 29th with 72,000 blood samples examined.

The report noted that half of adults 49 and younger have been exposed, based on the presence of antibodies. The infection rate progressively declined with age with only one quarter of samples from those over 65 years of age demonstrating antibodies.

By the end of November 2021, 103 million American had been infected.  With the emergence of the Omicron variant approximately 37 million new infections occurred during the subsequent two months.

High rates of infection were recorded in Wisconsin (56 percent) with descending rates in Georgia, Iowa, Illinois, Ohio, Wyoming and southern states.  Vermont had the lowest infection rate at 18 percent with higher rates in Hawaii, Maine, Oregon, Washington New Hampshire and Virginia.

With a high rate of exposure coupled with vaccination it is presumed that the level of immunity will contribute to a decline in the number of diagnosed incident cases. It would be of interest to determine the level of immunity among the 25 percent of the U.S. population that declined vaccination.  An additional concern is the relative duration of immunity acquired from natural exposure or from vaccination or their combination.  Present wisdom suggests that COVID has become endemic in the U.S. and that annual booster vaccination will be required concurrent with avian influenza to suppress seasonal outbreaks.