Safety Update – COVID-19


By Gary Gresh

Covid19. What is herd immunity?

Herd immunity happens when enough people have developed immunity to a particular infectious disease that the risk of further community transmission is either eliminated or significantly reduced.

What does it take to achieve herd immunity?

That varies by disease. For this particular coronavirus, doctors estimate that about 60% to 70% of the human population would need to have antibodies in order to have herd immunity as a species.

What is that COVID-19 estimate based on?

There’s actually a formula used to calculate that percentage (herd immunity threshold = 1-1/R0). This formula includes the basic reproduction number or “R-zero,” which indicates the average number of new people that a single infected individual can expose and infect. That figure for the flu is around 1.3, meaning that each infected person infects an average of 1.3 more people. Unfortunately, for the coronavirus, it’s between 2 and 3. So, this is a very contagious disease.

When will we achieve herd immunity against this coronavirus?

When we have a vaccine for COVID-19. Because we can’t just rely on natural immunity, or the kind that develops after you’ve been infected and recovered.

Right now, one study from Spain estimates that only about 3% of that country’s population has been infected. That figure is probably the same here in the United States. So, we’re still in the single digits, and it’s already putting a significant strain on medical systems worldwide. We probably need around 70% of the population to have developed antibodies in order to halt community transmission of COVID-19.