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Dr. Jennifer Rudd

Top 5 things to know about herd immunity and COVID-19

Thursday, February 11, 2021

Herd immunity. While this term is commonplace in my professional life, chances are these words rarely graced the dinner table prior to 2020. It is more settling to think of herds of cattle than herds of people. Yet, now we are immersed in a world where the fields of public health, epidemiology, and medical science surround us whether we like it or not. Here are the top 5 things I wish we all knew about herd immunity and the COVID-19 pandemic:

1. We achieve herd immunity through infections and through vaccinations.

An outbreak can end when we create roadblocks between people who have the disease and people who can get the disease. I suppose we could mass test every single person and physically separate these populations for a very long and indefinite time... but in a world where humanity thrives on connectedness, relationship and community, we should prefer to build those roadblocks through herd immunity when it can be safely achieved.  

To achieve herd immunity, we need enough people within a population that have pre-existing protection from disease to prevent spread of that disease. Your immune system must “see” either the virus or a part of it to build your own personalized immune cell army for future defense. Natural infection creates natural immunity. Vaccination also creates … (wait for it)… natural immunity. Either way, your own cells are doing the work to protect you from future disease.

2. We don’t exactly know the % required for herd immunity. 

Now, before you get too discouraged, hear me out a moment. This number is not some imaginary, magic guess. It is scientifically based, but it is largely dependent on what we want the end goal to be. Are we trying to eradicate this virus completely and rid the Earth of ever seeing COVID-19 again? That is unlikely — we have only done that a couple times before in the history of all history. Smallpox is the only human disease we have effectively eradicated from this globe.

Are we trying to knock this back from pandemic level to a typical seasonal virus, much like the flu? That will probably require 50-60% of the population to have immunity. What if we could take COVID-19 and push it back to a level like mumps? Or measles? Where it was uncommon enough to require reporting, tracing and public health interventions to prevent another large-scale emergence? I don’t know about you, but that seems like a great goal to me. We would probably need about 80% of the population with immunity to achieve that goal.

3. The available vaccinations for COVID-19 are good.

Are they perfect? No vaccine is. These vaccines were not rushed. Scientists were able to move through the trial phases faster because they are well-funded, and the process was streamlined to answer a very specific question: does vaccination prevent moderate to severe disease? The answer to that question is better than we could have ever dreamed with greater than 90% efficacy. The vaccines prevent death. They prevent hospitalizations, overwhelmed hospitals and overworked health care workers. They allow breathing room to get our kids back in school, our businesses fully opened and our most vulnerable to once again feel some community.

Don’t get me wrong — they can pack a punch. You can feel achy, sore and even a little feverish after vaccination. These are signs that your immune system is responding well. But the chances of a severe reaction are incredibly low; about 10 reactions per 1 million doses administered. In contrast, your chances of being hospitalized with COVID-19 are about 35-40,000 per 1 million cases. Your chance of dying from COVID-19 is about 15-20,000 per 1 million cases. That risk is much higher if you are older, if you have a comorbidity or if you are a part of a racial or ethnic minority group. Vaccination is the safest, most ethical way to achieve herd immunity. Hands down.

4. We aren’t there yet… but we could be there this year.

The race to herd immunity is more of a marathon than a sprint. I sincerely hope the worst is behind us. As the numbers of vaccinated people rise and winter changes to spring and then summer, we should observe our COVID-19 cases and deaths continue to drop steadily. As these numbers drop, we will be able to better contact trace and control new pockets of outbreaks. New variants of the virus may create some setbacks, but if we can stay true to our task and continue following masking and distancing guidelines, restricting large gatherings and encouraging vaccination, we can put the worst of this pandemic behind us and instead focus on what we want our end goal to be.

5. You matter.

You play a critical role in the trajectory of this disease. So much of our lives are out of our control. That can make you feel overwhelmed and discouraged, or it might make you feel apathetic and hopeless. I encourage you to let that stuff go and instead ask yourself what you CAN control. If you are hesitant to get vaccinated, educate yourself and ask questions. Identify unbiased, trustworthy sources such as the Centers for Disease Control (CDC), the World Health Organization (WHO), or personal acquaintances who are directly educated in the field of infectious disease and epidemiology. Follow public health guidelines by wearing your mask, washing your hands, and avoiding risky behaviors. 

Help an elderly friend or family member get vaccinated. Collect goodies for your health care workers. Raise money for teachers or for those who are struggling to make ends meet. Be creative and find ways to create community for those who are isolated or grieving. Don’t forget you are a part of something bigger. Be kind. Your community needs your positive light. I believe we can do this.

ABOUT THE AUTHOR: Dr. Jennifer Rudd is a veterinarian, researcher, and boarded microbiologist at the OSU College of Veterinary Medicine. She teaches infectious diseases to our veterinary students and is active in SARS-CoV-2 research. Due to her research, she is fully vaccinated for COVID-19.

MEDIA CONTACT: Mack Burke | Editorial Coordinator | 405.744.5540 |

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