COVID-19 clique immunity should be the goal

The COVID-19 “topic du jour” is herd immunity. When will it be achieved? What will it give us? How long will it last? Unfortunately, with enough people unwilling to be vaccinated, the hope for herd immunity in the near future appears dim. 

Herd immunity occurs when a sufficient proportion of a population is immune either naturally from infection or by vaccination, such that when rogue infections occur, they do not fuel epidemic growth of new cases, effectively dampening the spread of the disease. These infections remain isolated, with few new cases transmitted to others.  

The benefits of herd immunity are substantial: risk of widespread outbreaks and eruption of new viral variants are dampened. Although herd immunity is a population characteristic, every individual benefits, even those who are susceptible to infection.   

Herd immunity and individual immunity are inextricably linked. Achieving herd immunity requires a community-focused herd mentality, something woefully lacking in our nation at this time. As we all know, the American spirit is characterized by a fierce individualism demanding personal freedom and the right to choose for ourselves. However, when fighting the spread of an infectious disease, such a “me first’ mindset places others at risk. 

Herd immunity may require between 60 and 90 percent of the population to be immune. The most reliable way to acquire such a level of immunity is with vaccination. Those who have been infected may also be protected, though there is debate as to the level of antibodies they possess to protect them from reinfection, either with the same or a different variant.   

Unfortunately, millions of people are reluctant to be vaccinated due to concerns for vaccine safety or general vaccine skepticism. With over 100 million people now fully vaccinated, any rare adverse side effects have likely already occurred. Whether it is politics or personal preferences, getting to 90 percent of the population vaccinated will be exceedingly challenging in today’s social environment, where trust in both government and big pharma are commodities in short supply.  

If the nation cannot achieve herd immunity, the next best thing is achieving clique immunity. Clique immunity?  

In graph theory, a clique (pronounced to rhyme with “peak”) is a set of vertices all connected to each other by edges in a graph. Therefore, every vertex has one degree of separation from every other vertex. Clique immunity ensures that all people in a connected group are immunized. Pushing immunization campaigns down to the lowest possible level, be it cities, towns, communities, neighborhoods, or even extended families, will provide “clique” protection for such entities. This will create important pockets of immunity around the nation.   

When visitors carrying rogue infections seep into a clique, all clique members are protected. Clique immunity protects all people in the clique. Moreover, every person is motivated to add more people to their clique by encouraging vaccination, creating larger communities of clique immunity. Ideally, groups with clique immunity will expand and eventually overlap, moving towards the end goal of herd immunity across larger footprints of the population. 

Setting the objective of clique immunity for clusters of people is manageable. Families, neighborhoods, universities and companies can each aspire to clique immunity for their community, since they and everyone in their clique will benefit. Given the widespread availability of vaccines, and with both the Pfizer and Moderna vaccines moving towards seeking full Food and Drug Administration (FDA) approval, focusing attention on grassroots efforts to encourage vaccination will ultimately move the nation towards herd immunity. Clique immunity provides a convenient and imminently doable stepping stone along the way.         

Sheldon H. Jacobson, PhD, is a founder professor of computer science at the University of Illinois at Urbana-Champaign. He applies his expertise in data-driven risk-based assessment to evaluate and inform public policy and public health. He served as a member of the National Academy of Medicine standing committee for the Strategic National Stockpile in 2015-2017.        

Janet A. Jokela, MD, MPH, is the acting regional dean of the University of Illinois College of Medicine at Urbana-Champaign. She has served as an infectious disease and public health physician throughout her career.