In the course of this pandemic, health jargon has become part of many people’s everyday vocabulary. High school students know what an epidemiologist is. Those following the different coronavirus testing methods talk about PCR as if genetic amplification was commonplace pre-pandemic dinner conversation. In the soup of pandemic-speak, the phrase “herd immunity” has also popped up, first as a wishful solution to our unfortunate situation and later with all the seriousness of the outgoing White House behind it, as a proposed pandemic response.
For the sake of our vocabulary, but more for the sake of sound health policy, I invite anyone considering this approach seriously to imagine what that might look like in practice.
What is herd immunity?
When enough people in a community, the “herd,” are immune to a disease, the group is said to have herd immunity. And by immunity, we mean those who are personally immune can neither acquire nor transmit the disease. When enough people in a herd are personally immune, then the disease has difficulty spreading and the group achieves herd immunity. If someone in the herd, for health reasons, is not immune, their chance of getting sick is still small because spread within the herd is unlikely. Of course, if the person without immunity visits another herd without herd immunity, all bets are off.
In the last century, the health community observed that if enough children in a group were immune, epidemics of childhood diseases, like mumps, polio, or rubella, among others, could be avoided. For all these diseases, personal immunity, and sometimes herd immunity, was achieved through a vaccination campaign, not by getting sick and recovering.
The term herd immunity implies dependence on one another for safety. It requires the members of the herd do their part for the safety of the entire herd, especially for those who, because of certain limitations, cannot get personal immunity from vaccines.
The percentage of a community that needs to have personal immunity for the herd to be immune varies by disease. For the highly contagious like measles, 93 percent to 95 percent of the community must be immune. Infectious disease experts estimate that for COVID-19, at least 60 percent to 70 percent of the population would need to be personally immune to achieve herd immunity.
Why can’t we achieve herd immunity by spreading COVID-19?
Let’s start with the ethics of this question. To achieve herd immunity via the get-sick-and-recover strategy, over 60 percent of the population would need to acquire COVID-19 and recover. In Bexar County, that would amount to 1.2 million people. Compare that to the 80,000 plus COVID-19 positive people to date (I’ll do it for you, it is 15 times as many people). But it doesn’t end there. Behind the 1.2 million COVID-19 cases there would be human pain, hospitalizations, death, and devastating effects to our economy. If only a fraction of these persons needed hospitalization, we would still overwhelm the hospital system. If all metro areas followed the same approach, there would be nowhere to send overflow patients, and no place to ask for additional medical support.
At our current rates, 1.2 million infections would result in tens of thousands of hospitalizations and over 20,000 deaths. Also at our current rates, we would see Hispanic, Black, and elderly populations hardest hit by this get-sick-and-recover strategy.
After this mass extinction of San Antonians, we might well find that science outperforms the so-called get-sick-and-recover strategy. Studies so far indicate that COVID-19 immunity may be short-lived: Within two and a half months antibodies are no longer detected in the recovered individual in some cases. Early reports indicate that long-term impacts of COVID-19 are a true possibility. Months after recovering, some patients report chest pain and difficulty breathing. In more serious cases, patients experience complications with their heart, lungs, and kidneys.
Infections, hospitalizations, sickness, death, and long-term health consequences are what “herd immunity” through vaccination seeks to avoid. “Herd immunity” via infection is not a health policy. It would be a death sentence for thousands of San Antonians.
So what can we do?
Masks, when worn consistently and correctly, effectively reduce the spread of the virus. Mask-wearing and physical distancing work when we collectively take responsibility to protect one another.
Today, a vaccination for COVID-19 is on the horizon. That means vaccine-driven herd immunity may be possible. By this time next year, we may be able to enjoy the holidays with our extended family. However, let’s keep in mind, that will only happen if each of us takes responsibility for our herd: San Antonio. We can do that by getting vaccinated when the time comes. Until then we can take responsibility for our herd by keeping our masks on and remaining a safe distance when around those outside our household. Stay safe, San Antonio. We will get through this together.