There are a number of published reports and many people talking about herd immunity. What is herd immunity and what are some of the consequences of trying to reach it through natural immunity to COVID-19?
In South Dakota, it means there is the potential for more than 14,000 people to die.
Now that I have your attention, I will explain why.
Herd immunity relates to infectious diseases and the idea behind it is that a large enough percentage of the population becomes immune to the disease so that it becomes difficult to spread from one person to another. The percentage of the population that needs to be immune varies with the disease.
Highly infectious diseases, such as COVID-19, will require immunity among a large percentage of the population. Estimates for COVID-19 are that somewhere between 60% and 85% of the population will need to be immune. Since the disease will not just immediately stop once that percentage is reached, a larger percentage will actually end up becoming infected.
The 2019 census data for South Dakota shows almost 885,000 people live in our state. Taking into account what is needed for herd immunity, that means anywhere from 531,000 (60%) to 752,250 (85%) of the people in the state need to get infected.
Before I get to why those numbers are important, I want to share the two ways of achieving immunity. Immunity occurs either through vaccination or by having the disease. Currently, there is no vaccine for COVID-19 and it is not clear how long natural immunity lasts among people who have had COVID-19.
There are reports in the medical literature of people becoming ill with COVID-19 more than once and there also are some reports suggesting that antibodies to the SARS-2 virus that causes COVID-19 may decrease over time. It is true that the science is not clear, but it does indicate the possibility that long-lasting natural immunity may not be a sure thing.
Another important consideration is that there may be long-term consequences of COVID-19 in some people, even ones who were not initially very ill. The World Health Organization has issued warnings about possible long-term effects from being infected with COVID-19 and there are medical reports indicating possible long-lasting effects on heart muscle and the brain. Knowledge in this area is also developing, but should be considered when talking about achieving herd immunity via natural immunity.
Probably the most important consideration is that to achieve herd immunity without a vaccine, a significant number of people will need to be infected and that will lead to a large number of deaths.
Using current South Dakota data of individuals 20 years of age and older and the percentage of individuals with COVID-19 who die among this population, an estimated 14,200 deaths among South Dakotans aged 20 years and older will occur if 85% of them develop COVID-19. And yes, that does include deaths among young adults. An additional half a million South Dakotans aged 20 years and older may have long-lasting health effects.
Is that really worth not waiting for a vaccine? Isn’t it smarter to practice good hygiene and social distancing until we can minimize deaths?
Bonny Specker is a South Dakota mother, grandmother and epidemiologist. She is a professor at South Dakota State University.
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