SFH #151: The Endemic Era

Our future with COVID 🧐

Just over one-hundred and sixty million Americans acquired some form of immunity after getting coronavirus, the vaccine, or both. That's as of July of this year. This fall, you will start hearing more and more about us living with the virus as endemic like the common cold. Endemic viruses constantly circulate, ordinarily at low levels, but with sporadic, more severe outbreaks. Like the cold, we don't shut out these endemic viruses with quarantines, masks, and stay-at-home orders; we live with them. And we are about to live with the coronavirus in a comparable sense.

To understand more of what we are facing, I will try and do a simple breakdown of how our immune systems work, primarily through historical bouts of viruses.

Let's start with the flu. For nearly ninety years, survivors of the 1918 flu pandemic maintained strong antibody responses. And yet, we still get the flu roughly every five years as new variants come each year through rapid evolution.1 Each year, the flu acquires various mutations, keeping it agile enough to evade our T cells (our protective soldier cells that seek and destroy invaders). T cells are a crucial part of our adaptive immune response along with B cells. In a nutshell, our B cells produce antibodies to fight pathogens (ex: COVID), and our T cells directly kill other infected cells.2 These cells operate as the second line of defense behind our innate immune response, the first line of defense.3 What's important about understanding this operating system behind our immune response is that it's dynamic in how it helps us build resistance over time. Basically, our immune system has memory. Why does this 'memory' matter?

For that, let's look at measles. In a famous observational study from the Faroe Islands, a Danish physician named Peter Panum studied the outbreak of measles in the islands eight thousand inhabitants in 1846. He found that while measles mostly affected children on the mainland, it had a much different pattern on the islands. Untouched by outsiders and the pathogens that typically follow on Faroe, adults were more affected, although the elderly seemed to be the least harmed. His theory was that the measles outbreak from 1781 prevented this 'aged' generation from being affected (reinfected, to be precise). Panum's study demonstrated that our bodies learn to recognize pathogens we encounter. In some cases, we can hold on to those memories for decades, close to a lifetime with measles. Certainly, measles is a far cry from coronavirus as we hardly ever hear of an outbreak in modern times. In reality, Hawk just got his second MMR booster today in preparation for pre-K. Henry received his last polio, a virtually eradicated virus that infects the spinal cord. With more modern viruses, our lasting antigenic effects lessen, as with tetanus or diphtheria (bacterial toxins).

It is very early to truly understand the long-term immune response for COVID in the 'memory' regard. Indeed, the heightened state of the moment with variants, breakthroughs, vaccination hesitancy and political dividing lines on scientific evidence creates anxiousness, doubt, and fear. And how I can put my head on my pillow at night seeing the world go through this experience is trusting that science and evolution is the best history teacher here.

Immune resistance - through infection, vaccination and reinfection continue to weaken the virus on a grand scale. Surges with variants are scary, and stories of breakthroughs along with children dying are disheartening. And immunizations and contraction continue to build up our resistance to this pathogen. The more powerful our immune resistance, the more viral exposure we can endure without getting sick. This doesn't diminish the blow we've taken; it's plainly the reality we live in. Probability is stacked against eradication and herd immunity; the virus is too extensive and transmissible for that. The virus continues to circulate at low levels, and it spreads slower while infection and death rates are down drastically compared to last year. The variants are predominantly affecting unvaccinated people the most—which makes common sense. But the risk remains lower because of a collective immune resistance that continues to build. As we advance, COVID will become familiar, like the flu—one of the background hazards of daily life that goes through seasons and families. The worse effects will be behind us soon from a mass scale. Right now, it's just the bitter memory and the nagging tentacles of these variants reminding us of how bad the last 18 months of a once-in-a-century viral pandemic can be.

Now it's time for the endemic era.

Special thanks to Katherine Xue, my inspiration and source material behind most of this.4