Dr. Mark Kortepeter, a physician and biodefense expert who formerly worked at the U.S. Army “hot zone” research lab, explains why a policy of pursuing “herd immunity” for Covid-19 is a bad idea, unless it comes from a vaccine.
Before we get into that, though, here’s a brief primer on herd immunity: it’s a concept that usually applies to vaccines. The goal of achieving herd immunity is to vaccinate a high enough percent of a population to break the viral or bacterial chain of transmission between people. If enough people are vaccinated, the immunity of the “herd” of people protects those individuals who may not be able to receive a vaccine.
The percentage of the population that needs to be vaccinated depends on how contagious the infectious agent is. For measles, which is the most contagious virus known, up to 95% of the population must be vaccinated to achieve herd immunity. The SARS-CoV-2 virus (that causes COVID-19 illness) is not as contagious but estimates suggest that 50-70% of the population must be vaccinated to achieve herd immunity.
It is one thing to set a goal to achieve such a target level when using vaccines but trying to achieve this same level by allowing people to get infected naturally could be a disaster. Here’s why.
Other countries have already tried this, and it didn’t work.
Sweden pursued this measure and they had significant death levels early on. They continue to have one of the highest rates of death by population size across the world, despite being a small country. The UK also tried this and quickly gave up after they saw the devastation that occurred.
It’s impossible to protect those at highest risk.
One of the arguments is that we can allow younger people, who are at lower risk of severe disease or death, to become infected and they will create the herd immunity to protect others. This assumes that we can somehow protect the elderly and those with co-morbid illnesses (diabetes, hypertension, obesity, or other chronic diseases) who are at greatest risk for severe complications and death. The challenge is that the elderly are not all cloistered in long-term care facilities. They live among us, and children can serve as the vectors to bring the disease to those who are more vulnerable.
Others working in the community (teachers, professors, Post Office and grocery workers, for example) may be living with chronic diseases and have regular contact with younger individuals. The young can also be silent spreaders, which makes it difficult to determine who presents a risk to others. Even in a more protected environment, such as a long-term care facility, employees, who do live in the community, have served as the vectors to bring infection into the facilities.
Covid-19 infections may have long-term health consequences.
Thus far, we have measured the impact of the disease mostly in terms of numbers of fatalities or hospitalizations. However, every day we learn new things about COVID-19. Already we are aware of a rare Kawasaki-like multi-system inflammatory syndrome that occurs in children. We are also learning more about its potential devastation, even in those who have asymptomatic infection.
We know this virus affects multiple parts of the body beyond the lungs. Recent reports suggest that some college athletes infected with coronavirus show evidence of myocarditis, which is inflammation of the heart. When someone’s heart becomes inflamed, they can have rhythm disturbances, sudden death, or heart failure. We won’t know the long-term consequences of such a finding for some time.
Others who have been infected and recovered have complained of chronic fatigue, skin rashes, headaches, etc. The bottom line is that we don’t fully understand the implications of infection with the SARS-CoV-2 virus, but it does not appear to be as benign, even in the young, as we once believed. Why does a 22-year-old without medical problems get severe illness requiring life support, whereas an 80-year-old has mild disease? No one has a clue.
When we take our foot off the brakes, the virus runs rampant.
The U.S. has had over 6.5 million documented cases of infection and over 194,000 deaths thus far. Even if you estimated ten times as many (62 million) have already been infected, do we really want to see that number reach half or 70% of the US population of 328 million to reach herd immunity? That would translate to 164 – 230 million infections. My own back-of-the-napkin calculation with a proportional increase in deaths translates to 497,000 – 696,000 deaths. Others have come up with estimates of over 1 million deaths. None of those numbers incorporate the additional impact of lost productivity, ongoing disruption of societal activities (work, schools), or numbers of hospitalized.
So, the last thing we want to do is just allow the population to become infected to try to achieve herd immunity. It is much safer to achieve that goal through vaccination.
Keep in mind, that the best thing we can do is shut down ongoing spread now. That is the ultimate key to allow everyone to move back to “normal” interactions, work, and opening of schools. We don’t need to wait for a vaccine to achieve that – it is within our power to control. It comes down to following the measures repeated over and over again by me and my public health colleagues – wearing masks, maintaining distance from others and hand washing. The states and countries that have taken the threat seriously have managed to do this.
Until then, we will continue to play “whack a mole” catch-up as the virus takes any advantage it can to spread when we give it an opening.