43% of Americans—140 million—have had COVID, CDC estimates

According to the latest analysis by the Centers for Disease Control and Prevention, an estimated 140 million people in the US have had COVID-19.

The total number of cases reported by the CDC at the end of January was 74 million. Many COVID-19 cases are not reported or detected, so these numbers are expected to differ. The undercount of actual infections is expected to be significant. Some people can be counted more than once if case reports include infections in people who have tested positive multiple times.

Over time, the CDC has been estimating the number of infections from the omicron variant. The CDC estimates that 37 million people were affected by the coronaviruses in December and January. The number of cases reported to the CDC was around 26 million.

There were nearly 72,000 blood samples tested in late December and early January for the infections. The program uses blood samples sent to commercial labs for non-COVID-19 related testing. The samples were surveyed for the antibodies from the disease.

Infection and protection

The CDC uses blood donations to look for antibodies from both past and current infections. The data from that system was last updated in December. The CDC estimated that about 95 percent of people aged 16 and older in the US had an immunity to the coronaviruses.

The omicron variant caused the largest surge of cases so far. The tests do not show that people are protected from infections. The tests only detect the presence of antibodies, they don't measure the strength of protection. It is difficult to estimate how much protection there is in the population based on the data from the past.

Over time, cell-based immune responses from past infections and vaccinations will provide more sustained protection from severe disease, hospitalization, and death. The relatively lower rates of hospitalization and death seen during the surge of omicron cases are likely to be explained by the 95 percent seroprevalence estimate from December.

The data shows the success of vaccination and the higher death rate in older people. When the data is spread out by age, older groups with the highest levels of vaccination and higher risks of death have the lowest rates of past infections. The CDC estimates that only about 37 percent of people in this age group have had COVID-19, which is a vaccine. Children under the age of 5 are ineligible for vaccines, so they have the highest rate of infections.