Study: US COVID cases, deaths far higher than reported

Study: US COVID cases, deaths far higher than reported Antibody testing shows that 14% of Americans had been infected by Nov 15, and 35% of deaths were missed. CIDRAP

An estimated 14.3% of the US population had antibodies against COVID-19 by mid-November 2020, suggesting that that the virus has infected vastly more people than reported—but still not enough to come close to the proportion needed for herd immunity, according to a study published today(Tuesday) in JAMA Network Open.

In the cross-sectional study, researchers from study sponsors Pfizer and Merck analyzed data from random community seroprevalence surveys and five such regional and national Centers for Disease Control and Prevention (CDC) surveys to estimate infection underreporting multipliers. Seroprevalence surveys reveal the proportion of a population that has antibodies against a certain disease, such as COVID-19.

After adjusting for underreporting using validated multipliers, the analysis revealed an estimated median 46,910,006 infections with SARS-CoV-2, the virus that causes COVID-19; 28,122,752 symptomatic infections; 956,174 hospitalizations; and 304,915 deaths from April to mid-November.

According to those numbers, 14.3% of Americans had been infected with the novel coronavirus by Nov 15, 8.6% had symptomatic infections, with an infection-hospitalization ratio of 2.0% and a case-fatality ratio for people with symptoms of 1.1%.

In contrast, the CDC reported 10,846,373 COVID-19 cases and 244,810 deaths in that same time span, with 1,037,962 cases recorded in just the last 7 days of that period (on average, 148,280 new daily reported cases).

Estimated 35% of COVID deaths unreported

The authors noted that seroprevalence surveys are essential to monitoring progress toward herd immunity, which occurs when roughly 60% of a population has antibodies that can help slow community transmission. In comparison, reported case numbers are underestimates due to many symptomatic people not seeking testing or medical care and the estimated 40% who have no symptoms.

"The US population remains a long way from herd immunity even with millions of new infections each week," the researchers wrote. "The number of estimated COVID-19 deaths is also remarkably more than the reported deaths in the US through November 15, 2020, supporting the conclusion that approximately 35% of COVID-19 deaths are not reported."