Herd Immunity

Transcript

Because most emergency department visits last a lot longer than a standard office visit, it gives emergency physicians an opportunity to talk to patients and families about a lot of different things. And as the amount of information about COVID-19 continues to evolve, so too does the conversation in the general population. One of the more recent popular conversations centers around a phenomenon known as herd immunity. This term is an infectious disease term that refers to the concept that an infectious agent becomes far less threatening to a species because large numbers within that species become immune to the infecting organism. In general, the two ways that our living organism becomes immune are through exposure with infection and through vaccination. In other words, in the context of COVID-19, immunity is acquired through either being infected with a virus and surviving the infection, or being immunized once a vaccine is developed and available to the public. Herd immunity is also affected by what is known as the R0 number, which is a mathematical symbol for what is known as the basic reproduction number.

This number is an indirect measure of infectivity. In other words, the number of individuals that it is believed that a single infected person will subsequently infect themselves. The higher this number, the more easily transmissible the disease and the greater the number of likely infected people will be. And in the context of COVID-19 and herd immunity, the higher this number, the more individuals that are going to be required globally to reach the threshold of herd immunity. For example, measles, one of the most infectious diseases on earth, has an R0 number of 16, suggesting that as many as 90% of the global population would have to become immune either through being infected and surviving or being vaccinated in order for herd immunity to occur. Because the R0 number for COVID-19 is believed to be around 2, it would suggest that approximately 70% of the world’s population would have to be immune in order for herd immunity to occur. Some have suggested that herd immunity is the answer. Even in the absence of a vaccine. This is incorrect because it would require that nearly 70% of the world’s population would have to become immune through infection. Meaning that approximately 6 billion people on earth would have to become infected, of which nearly 2% would die. This staggering number of deaths is the main reason why herd immunity and the absence of vaccines is not acceptable.

Immunologists, epidemiologists, and other clinical experts agree that herd immunity is not the answer unless we can vaccinate individuals against COVID-19, which is why, while we are waiting for the vaccine to developed, we are still going to continue to practice all of the things that we’ve been learning. We’re going to stay indoors, unless we absolutely have to go outside. We’re going to practice social distancing and all of the other practices that we’ve learned over the last several weeks, so that together we can work to flatten the curve and decrease transmission.