Thinking Out Loud: China and the Hygiene Hypothesis

Let’s start with an assumption that the number of cases of COVID in China is difficult to determine, primarily because China doesn’t care to share. So most of the numbers I have read and may mention come to us indirectly.

You might think of this piece as a companion to the one I wrote on Sweden, which chose to minimize lockdowns. Undoubtedly, China’s Zero-COVID was the antithesis, the ultimate in lockdowns, testing, and tracing. One need only search on YouTube for videos showing entire apartment buildings shuttered; their occupants quarantined to know that China minimized exposure to COVID. Their vaccination program has been extensive, but to the best of our understanding Sinovac, the Chinese vaccine, is half as effective as our mRNA vaccines.

According to reports, last week, on one given day, the official number of new Chinese cases stood at 3,049; according to unconfirmed reporting to the Chinese National Health Commission, the number was 37 million. The estimated number of new cases over the 20 days since Zero-COVID ended is roughly 18% of the Chinese population- 250 million. Over the past week, the definition of a COVID death has been narrowed to be a respiratory death with a positive test for COVID, so deaths from COVID-related complications may be missed. Given the disparity between three thousand and nearly 40 million, those cases might be considered a rounding error.

Suffice it to say COVID is now rapidly spreading across China and putting a significant strain on their healthcare system. It should also be evident in lifting the lockdowns that they had worked very well in limiting the spread of infectious disease. But unwinding lockdowns is as difficult as imposing them.

COVID’s rapid spread is because China’s population is essentially naïve, unexposed to any of the COVID variants – they practice “sterility.” With respect to the hygiene hypothesis, they are people inside a bubble whose defenses are not immunologic but physical. When that physical barrier is removed, the immunologic system has no experience with the pathogen. China is now experiencing what most of the globe experiences in the winter and spring of 2020.

Advocates of the hygiene hypothesis might argue that if they had simply protected the most vulnerable and allowed the virus to spread across the population, they would have a far more vigorous immunologic defense than they currently have. Or perhaps if they had staged the end of lockdowns by some form of prioritization, the least vulnerable first, they might have reduced the hospitalizations and deaths. Of course, releasing the least vulnerable does not necessarily mean fully opening up society. Are first responders or essential workers necessarily the least vulnerable?

The advocates of the Great Barrington Declaration might now be pointing to this same data as proof of their beliefs. But before accepting that argument, we must remember that the Great Barrington Declaration had the advantage of hindsight – we had already begun to identify the most vulnerable. And I hasten to point out that they were not the usual suspects; it did include the frail and elderly, but unlike influenza, not the kids. An across-the-board lockdown makes some sense when you cannot identify the most vulnerable. And remember, in those early days when we thought the plague had returned, everyone was keen on being vulnerable and, therefore, at the front of the line for protection, be it hospitalization or vaccination or deemed “essential.”

The hygiene hypothesis suggests that if we could have more readily identified the vulnerable, we could have allowed the others to become ill. Granted, there would still be deaths and hospitalizations, but statistically, they would be far fewer than those vulnerables. We have done that experiment here in the US, resulting in more deaths among the unprotected than the protected. However, unlike China, going without protection, in this instance vaccination, was their choice. We will not have a definitive measure. Excess mortality is a rough approximation, but given China’s political decision not to share information in a global pandemic, any conclusions will remain contentious. China is not a good neighbor; their decision to “save face” makes understanding more challenging, and keeps that knowledge only for themselves.