Study: No COVID-19 Herd Immunity from Previous Common Cold Infections

Back in the summer, some tentative research suggested that prior infections with the four coronaviruses associated with the common cold might confer some protection against the COVID-19 virus. Based on these findings, some scientists speculated that the threshold for COVID-19 herd immunity was low and could be soon reached. In other words, they thought the pandemic could be over sooner and ultimately be less lethal than many feared.

Unfortunately, a new study in the journal Cell suggests that hope was unfounded.

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. Epidemiologists generally estimate that the COVID-19 threshold for herd immunity is around 70 to 90 percent.

It’s now pretty clear that the herd immunity threshold could not be as low as some of those researchers hoped. Otherwise, the northern hemisphere would not have seen a winter surge in COVID-19 diagnoses, hospitalizations, and deaths:

Now the Cell study undermines the hypothesis that prior infection with common cold coronaviruses provides a substantial protection against COVID-19 infection. University of Pennsylvania researcher Scott Hensley and his colleagues tested blood samples taken from people prior to the onset of the pandemic for antibodies to the common cold coronaviruses. These w