Just read a fascinating snippet in the JAMA Journal (Journal of American Medical Association). Yes, that’s where I go when I want to zone out. It’s like my media comfort food.
Anyway, I hear herd immunity bandied about all the time during this pandemic. Since I have a degree in epidemiology, I’ve always associated the term with vaccinations and threshholds but was never sure if this would help us conquer Covid.
The author of this article summarized the definition so well. “The herd immunity threshold is defined as the proportion of individuals in a population who, having acquired immunity, can no longer participate in the chain of transmission. If the proportion of immune individuals in a population is above this threshold, current outbreaks will extinguish and endemic transmission of the pathogen will be interrupted.”
What this means, simply, is that if X percentage of a total population has been sick with the illness, or receives the vaccine so they won’t get the illness, then even if some people get sick, they won’t be able to infect enough other people to make the illness spread so quickly.
The question is, what is our X percentage for Covid-19? So, it turns out that right now, between 50-67% of the population would need to be infected/vaccinated with this coronavirus to create a “herd”.
For Israel, current population 9.4 million, 6,298,000 would need to be infected or have been ill to bring us to 67%. Right now, we are at about 3.25%.
With the 0.5% overall mortality rate that Covid-19 seems to create, that would mean an additional 29,000 people would need to die to reach this percentage.
I don’t think herd immunity is in the cards for us, right now. We will need to find another way to live with this new virus.
Thanks for the interesting thoughts on herd immunity!
However, what about the fact that kids rarely experience adverse effects from COVID, and also the fact that cases may be higher than what is reported, especially if they are in children or individuals who had no or mild symptoms, and therefore did not even test for COVID?
Plus, is the 0.5% mortality rate that you refer to applicable to Israel, or is it a global rate?
Thoughts to ponder…what’s your take?
thanks for the thoughtful questions! Herd immunity is based on known transmission rates, so it’s not so affected by adverse effects or asymptomatic cases. And yes, the .5% mortality rate is global. Israel’s is lower.