Americans Are Nowhere Near Herd Immunity to COVID-19

We are nowhere near achieving COVID-19 herd immunity according to a new study in the journal JAMA Internal Medicine. The researchers reached this conclusion based on an analysis of routine blood tests sent to commercial laboratories through the end of September taken from nearly 178,000 people in 52 U.S. jurisdictions. In this seroprevalence screening study, the researchers are seeking to detect what proportion of Americans have developed disease resistance antibody proteins produced by the immune system in response to infections by the COVID-19 virus. The study relied upon the results of routine blood tests while excluding tests taken from patients suspected of having COVID-19.

Herd immunity is the resistance to the spread of a contagious disease that results if a sufficiently high proportion of a population is immune to the illness. Some people are still susceptible, but they are surrounded by immune individuals, who serve as a barrier preventing the microbes from reaching them. Herd immunity is generally achieved via mass vaccination. An accompanying commentary by three public health researchers noted, “Unfortunately, history has shown that although herd immunity resulting from infection can curb pandemics, it does not eradicate diseases.”

Earlier in the pandemic, various researchers made speculative calculations (many of which I reported) suggesting that COVID-19 infections were much more prevalent tha