The Uncanny Delta Wave

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July 19, 2021 10:26 a.m.

There’s no longer any question. We’re in the midst of a wave of new COVID infections, driven largely by the highly contagious Delta variant. Little more than a month ago Israel’s daily case count was in the single digits. It’s now crested over 1,000 a day. Great Britain has seen a similar trajectory and cases counts are rising rapidly in almost every US state. And these are only the parts of the world that have the luxury of widely available vaccines. But in those highly vaccinated countries, the chained relationship between infection, hospitalization and mortality has also clearly been broken. So are we heading back to something like we saw in the Spring of 2020 or the winter of 2020-21 or are reacting to infection numbers in a way that is simply outdated in the context of widespread vaccination?

Many public health experts and officials will tell you that this is the point of vaccines: to prevent death and serious illness, not notional infections which may cause no symptoms at all. Indeed, there’s a real debate about what constitutes infection or cases of COIVD. COVID can briefly take hold and reproduce in a person’s nasal cavity and upper respiratory system before being knocked down by effective vaccines. That will produce a positive result on a PCR COVID test. But it’s an open question whether we should be treating that as an infection or a case of COVID for the purposes of setting public policy or judging our success in emerging from the pandemic.

Some Key Questions

Are fully vaccinated people getting COVID? Is the Delta variant reducing the very high efficacy recorded in the initial trials?

This turns out to be a really difficult question to answer – both because the information is hard to track down and because it’s not clear in many cases whether the information even exists. We’re seeing more and more anecdotal cases of fully vaccinated people testing positive. The UK’s new health secretary Sajid Javid just tested positive. Each day brings news of another positive test at the Olympic village in Japan. But how many of these cases are symptomatic or more than very mild? I’ve tried to track this as closely as I could and the information is actually pretty hard to come by.

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Virginia is one state that has a clear dashboard breakdown of “breakthrough” cases. To get a look at this question, I set the date range from June 1st through July 9th. Earlier in this calendar year there was little to no Delta variant and far fewer people were vaccinated. So it’s apples and oranges. According to this data, 97% of the new cases have been in people who weren’t fully vaccinated. For hospitalization, it’s 95% and fatalities it’s 93%.

Pretty good case for getting vaccinated!

But how do we square this data with data out of Israel showing something like a third to one-half of cases are vaccinated? One big explanation is likely the nature of testing. The testing in Israel looks closer to surveillance testing, where you’re testing a lot of people who weren’t feeling sick. In most US states, people are only getting tested if they feel sick. And that especially goes for people who are vaccinated.

What About Long COVID?

There’s no question that mRNA vaccines radically reduced your chances of getting seriously ill or dying from COVID. Going back to the Virginia data, 47 people died of COVID in the state between June 1st and July 9th. 1 had been vaccinated; 46 had not. But aside from dying in a hospital, what are the risks of getting COVID if you’re vaccinated? Specifically, what about ‘Long COVID’?

As we’ve learned a significant minority of COVID patients have symptoms that last long after the 2 or 3 week period of active infection. Many of them appear to debility or health damage which is either longterm or permanent. Long COVID appears correlate strongly with severity of illness. But there are also many examples of long COVID suffers whose initial cases were mild or at least not severe. So are breakthrough cases that are very mild or even asymptomatic causing long COVID? Or to put the matter differently, are the mild or asymptomatic cases which do occur among the vaccinated, albeit at a much lower rate, causing any longterm health consequences?

If you’re vaccinated and run the risk of getting a very mild or asymptomatic case, if there are no health consequences beyond at most a couple weeks, why does it even matter? Are the asymptomatic or very mild cases which do occur among the vaccinated generating any meaningful health consequences and are those people spreading the disease?

Those are questions which matter individually for vaccinated people and how they make their own personal decisions about risk. But they also matter a lot for setting policy at a macro-scale. And they’re both questions we don’t clearly know the answer to yet.

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