Let’s do a quick math: herd immunity requires minimum infection rate of 70%. Take US population as 300 million, so this means 210 million people infected. Assume a minimum mortality rate of 1%, the total number of death will be 2.1 million. However, the prerequisite of the 1% mortality rate are:
- No collapse in the medical system
- Sufficient supply of materials
- Stable social order
- Stable economy and stock market and
- Efficient government operation
Otherwise mortality rate of almost 10% in Italy would be a reference. After herd immunity was over, will the US still be able to maintain its dominance in the world?
As President Trump mentioned in a press briefing that the U.S. coronavirus death toll could have reached 2.2 million without social distancing restrictions, and it would signal “we all together have done a very good job” if the number was limited to 100,000–200,000.
Take Italy as an example, which is currently closest to herd immunity (according to available truthful data). The Italian population is about 60 million, herd immunity will mean an infection of 42 million, with mortality rate of 10%, the death toll would be 4.2 million. Right now, infection case is about 100,000 in Italy. Considering increased number of testing and asymptomatic cases, a maximum of 6.4 million people may have been infected, which is still far away from 42 million people.
Presently most countries have adopted lockout and the infection curves have flattened. So it may take many years for the infection rate to reach 70%. If lockout was removed, which appears only a matter of time, the real infection curve could head upward again.
On the other hand, what if herd immunity did happen in Italy but not its neighbors like Switzerland, Spain or France? Should they continue to shut down the entire country and build a wall on the border?
Furthermore, human understanding of Covid-19 is still simple and lack of imagination. As the strangest virus in human history, it has refreshed horizons of human beings in just a few months. What if antibody of the virus had a limited duration, the virus mutated, or the virus suddenly disappeared? Hundreds of thousands of people would have died in vain?
The only hope for herd immunity are vaccines and specific medicines, but we all need to prepare for the worst.