COVID Transmissions for 7-7-2021
Does Pfizer still work against Delta?
Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions.
It has been 598 days since the first documented human case of COVID-19. In 598, Chinese emperor Wendi lost almost 90% of his nation’s army and navy in a disastrous war. And I thought 2020 was bad.
Welcome back! The 4th of July passed her in the US without great consequence in my own household, but was a welcome break from that has turned out to be quite a busy summer so far.
The Delta variant of COVID-19 is rising to global prominence, with serious consequences. Today we’ll discuss its rise to dominate US COVID-19 cases, and an Israeli result regarding Pfizer vaccine efficacy against this variant.
Bolded terms are linked to the running newsletter glossary.
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Now, let’s talk COVID.
Delta (B.1.617.2) variant is now the dominant lineage in the US
Predictably, the Delta variant has become the dominant lineage in the US, reflecting some kind of fitness benefit that this variant appears to have evolved. The CDC announced this yesterday: https://www.npr.org/sections/coronavirus-live-updates/2021/07/06/1013582342/delta-is-now-the-dominant-coronavirus-variant-in-the-u-s
If you are vaccinated, and you live in a highly vaccinated area, all other things being equal, I don’t think you really need to worry that much about this. However, there is still a large population of people who are not vaccinated and who live in areas with large unvaccinated populations. Those people are at risk of death or serious complications due to COVID-19, and they don’t have to be. They are at greater risk because Delta is out there, and there are behaviors they need to adopt in order to protect themselves. One of those behaviors is getting vaccinated.
I recognize that there have also been some recent data suggesting that mRNA vaccines (specifically Pfizer) may not work quite as well against this variant. Let’s talk about that next.
Israeli results with Delta variant and vaccines—don’t be so hasty
It has been widely reported that an Israeli study has demonstrated that the Delta variant has evolved the ability to meaningfully evade immunity induced by the Pfizer vaccine. The study, which has not actually released any results directly, was quoted as showing top line results with 64% vaccine efficacy against disease, 93% effectiveness against severe disease and hospitalization. Here’s CNN’s story on it, one of many: https://www.cnn.com/2021/07/06/health/israel-pfizer-efficacy-delta-variant-intl/index.html
I’m skeptical of anything that is labeled as “top line” without details, or of results that are given in a statement without an accompanying paper. But I’m particularly skeptical when a leading institution in the country releases a statement that it is too early to make any kind of assessment—which the Hebrew University did shortly after the government released these top line results.
The thing about scientific data is that it can be misleading if the appropriate follow-up time is not given. This variant has not be spreading in Israel for a very long time at all. It seems to me that it must be less than two months, a number which I chose in particular because it was the amount of follow-up time that was included in the original clinical trial of these vaccines. Clinical trials are based on the analysis of disease as a random event, so if follow-up times are not carefully considered, the results can be hard to interpret. Take an example—you are having a coin-flipping competition (imagine that in this story you are VERY bored due to a global pandemic), and you flip two coins which both come up tails. If you stop there, you have a coin that gets tails 100% of the time. Your choice of follow-up here is clearly flawed; if you had continued for a more appropriate number of flips, you would have eventually found the true frequency of heads or tails for this coin. but you didn’t give it that follow-up.
I suspect that the Israeli results have this issue. However! Let’s look at what these results imply. The situation here shows vaccine efficacy that is well above the 50% threshold that was originally desirable for COVID-19 vaccines. Beyond that, the chances of hospitalization or severe disease remain substantially reduced. Even without the details of methodology, this doesn’t actually sound so bad. Other data from the UK have showed approximately 80% to 90% efficacy of the Pfizer vaccine against disease from this variant, so there is also that to be considered.
However, I also want to make a point about how trial conditions can impact data. When clinical trials for these vaccines were conducted, the context was one of a prevaccine world. Widespread business closures, masking, and extreme social disruption were all features of everyday life. In the vaccinated world, countries have begun to lift these sorts of restrictions. Israel, for example, began really relaxing restrictions in June. It is very possible that relaxation of restrictions is contributing to this preliminary effect.
Human behavior is a factor in everything to do with disease. It is not “the Delta variant” causing these cases. It is, as virologist and journalist Alan Dove put it, non-immune people breathing on each other causing these cases. Perhaps the Delta variant is more likely to be able to infect people who believe themselves to be immunized, but the virus itself is not doing this. People are doing this. We have to consider the human element of this equation. Alan’s tweet here:
Keep this in mind when you think about any results to do with Delta or any other variant.
What am I doing to cope with the pandemic? This:
Having guests
In normal times, I’d find it hardly worth telling you that this past weekend, my wife and I had a guest stay with us. This person, a newsletter reader in addition to a friend, is a US citizen living abroad who returned here to get vaccinated. This visit coincided with the period after the second dose of that vaccine course, but was also made more reassuringly secure by the use of a European antigen-based COVID-19 test. Here’s a photo of the general type of thing, gifted to me by this reader:
These things are great, and we need them to become more commonplace in the US. If everyone used one of these every day—vaccinated or not—and stayed inside if they tested positive, we could really see COVID-19 go away. But they’re not widely approved here and they’re a bit too expensive here to be affordable on the daily. The ones on offer here in the US are around $20, which is even more expensive than the much-maligned avocado toast. Realistically, that’s more than 2 hours of minimum-wage work, which is a huge problem. We need to make the price of these things come down, and we need to do it before the fall, when surges in COVID-19 cases are expected.
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No corrections since last issue.
See you all next time. And don’t forget to share the newsletter if you liked it.
Always,
JS