Global Health Experts Warn Against Herd Immunity Approach to Covid-19

In an open letter, 80 health experts call the approach ‘a dangerous fallacy unsupported by the scientific evidence’

Photo by Mika Baumeister on Unsplash

Herd immunity has received significant attention since the beginning of the Covid-19 pandemic. Several countries hoped that herd immunity would offer protection against the virus, and some even went so far as to loosen restrictions to allow for the natural spread of the virus. In an open letter published today in The Lancet, dozens of health officials publicly criticized herd immunity approaches to slowing Covid-19 as flawed and dangerous.

Herd immunity relies on an adequate number of immune individuals within a population such that a pathogen is unable to spread. Beyond that, herd immunity differs widely from one disease to another. Vaccines offer a powerful example of how herd immunity can control the spread of a disease. For example, a measles vaccination rate above 95% is sufficient to halt the spread of the measles virus.

However, reliance on herd immunity for a disease such as measles is underscored by years of scientific data that supports the efficacy of the vaccine, and the durability of immunity conferred. Just seven months into the Covid-19 pandemic, this level of scientific certainty is lacking.

The 80 authors of the letter published today in The Lancet argue that herd immunity approaches to stopping Covid-19 are deeply flawed and potentially dangerous.

The herd immunity approach to stopping Covid-19 can best be explained as allowing the virus to spread within low-risk populations — namely younger populations — to the point where enough people have caught the virus and developed immunity that’s sufficient to protect high-risk populations such as older adults.

However, as the authors of the letter underscore, one flaw to this approach is that the durability of Covid-19 immunity after an infection is unknown. At this point, researchers have not been able to demonstrate conclusively that antibodies from Covid-19 offer lasting protection.

Beyond this, recent outbreaks of Covid-19 have been linked to younger populations, including those who are asymptomatic…