The notion of herd immunity is at the center of discussion about global vaccination efforts and the next steps in fighting the Covid-19 epidemic and bringing the economy back on track.
In order for the epidemic to stop, the coronavirus has to run out of susceptible hosts to become infected. Animal husbandry immunity occurs when enough people in a population develop immunity through previous infections or vaccinations, so that the virus does not spread easily and even those who are not immune are protected.
To reach herd immunity to covid-19, public health officials estimate that approximately 60% to 70% of a given population will need to develop an immune response to the virus. Some pathologists and mathematicians now say that the effect of the herd may begin at that stage, suggesting that potential protection may be achieved sooner.
Nonetheless, infectious-disease experts are relentlessly warning against the idea of trying to reach herd immunity to coronavirus without a vaccine, as the cost to human life would be surprising and if it did not happen at all soon.
Even with a single vaccine, there will still be obstacles to achieving herd immunity. “It’s an ongoing process,” said Saad Omer, director of the Yale Institute for Global Health. “You can start watching [an effect] Before that threshold, but the other point is that it will still erupt on a small scale. “
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