COVID Transmissions for 10-21-2020
Good morning! It has been 339 days since the first documented human case of COVID-19.
The headlines section today is dominated by one piece, which neared the length of a mini-In Depth. Also, responding to a reader comment in the talk back section.
As usual, bolded terms are linked to the running newsletter glossary.
Keep the newsletter growing by sharing it! I love talking about science and explaining important concepts in human health, but I rely on all of you to grow the audience for this:
Now, let’s talk COVID.
A vaccine “challenge trial” is planned to start in January
It was announced recently that a “challenge trial” will begin in January to test a new vaccine against COVID-19: https://www.nytimes.com/live/2020/10/20/world/covid-19-coronavirus-updates/a-human-challenge-trial-will-begin-in-january-in-which-volunteers-are-deliberately-exposed-to-the-virus
A “challenge trial” refers to a clinical trial in which subjects are deliberately infected with the agent being studied. In this case, healthy volunteers in the UK will be given COVID-19 on purpose, ultimately towards the goal of testing a new vaccine.
There is a lot that we can learn from such a trial. For example, researchers will be looking into the minimum infectious dose of SARS-CoV-2 in humans. That alone will be a very useful finding in terms of understanding human transmission of SARS-CoV-2.
There will also be a better understanding of the natural history of disease, the immune response, and many other questions that can be investigated in this trial setting.
I also happen to think it’s totally unethical to conduct this trial at this time.
Earlier in the pandemic, when it still appeared that COVID-19 was largely a phenomenon occurring in China and Italy, I believed that observational challenge trials, if started right then, could have real benefits for our ability to fight the pandemic. At the time, I thought that trials in young, healthy volunteers would help us better understand transmission of the virus and the healthy immune response to the virus and would also create a small immune population who could be useful for the pandemic response. At the time, I thought such a trial could be worth considering as a way to try to prevent the pandemic from taking root around the world.
Ultimately, my considerations were pointless. Due to a number of policy failures, the experiment I was describing was conducted after all—on a global scale in a variety of countries. We have gotten numerous results that have taught us the answers to many of the questions that, earlier in the pandemic, I was interested in answering as a means to save lives.
A challenge trial at this time doesn’t make any sense to me. Normally you conduct a challenge trial under several of the following conditions:
The disease you are studying has predictable outcomes that are not severe
The disease you are studying is relatively rare or its occurrence is unpredictable
There is a readily available therapeutic for the disease that is extremely effective
It is clear that patients understand the disease that they are going to be infected with and the potential consequences of getting it
For example, noroviruses, which cause short-lived gastrointestinal illness, might qualify here because norovirus outbreaks occur intermittently, the viruses themselves are rarely fatal in healthy volunteers, there is an easy treatment protocol that is highly effective, and it’s easy to explain to patients what they are likely to experience and what the consequences may be. I’m not an expert in noroviruses so it’s possible there is some mitigating circumstances with them that makes them a bad option for a challenge trial—I just think they’re a relatable example.
By contrast, COVID-19 is not a disease with predictable outcomes. We do not know why some young people die of it. It is not relatively rare; 8 million people in the US alone have had it, along with more than 20 million worldwide. We do not have universally effective treatments for COVID-19, by any means. Finally, since scientists do not fully understand COVID-19, I really don’t think that it’s possible for patients to provide informed consent for this trial. I wouldn’t be able to explain to a patient what risks they might be running.
Based on that, I don’t see a reason to conduct a challenge trial and I don’t see ethical justification for it. People could die from this, when there is the alternative of conducting a field trial—one where patients are given a vaccine and then the frequency of COVID-19 in those patients is measured based on their normal lives “in the field.”
I will concede that we could learn more from this challenge trial, but I’m not sure that the cost is justified when, for the entire length of this trial, people out in the world will be getting COVID-19 and dying from it. We might as well conduct the trial out there, and hope to protect some of them, than go ahead with a challenge trial format.
What am I doing to cope with the pandemic? This:
Smashing Pumpkins
Today I watched the following video, which was a really nice change from nearly all other nonfiction video I’ve seen recently:
Today I received the following comment from reader Robert Berger:
I tested positive for Covid-19 first week of April. I tested positive for antibodies in May. I tested positive again for antibodies last week. Which is more likely:
1. My body continues to produce antibodies a half year after I was infected?
2. I was infected a second time, and my body produced antibodies against the second, more recent, infection, resulting in my being asymptomatic?
Here’s the answer I gave:
Great questions, Robert!
I think there's not enough information to give a definitive answer, though. One thing worth keeping in mind is that there is substantial individual variation in terms of antibody responses, and any decay in your antibody levels would begin around the time that your infection truly resolved, something that I'm not sure we can currently measure.
It's possible that you have maintained detectable antibodies this entire time, particularly if you had a strong immune response.
It is also possible that you experienced a reexposure and fought off a second infection with SARS-CoV-2.
One way to obtain a clue as to which it is would be to compare the levels of SARS-CoV-2 antibodies that were detected in your blood in both your test in May as well as your recent test. If the test in May had higher levels than the recent test, I would say both possibilities are still on the table. If the recent test had substantially higher levels than the test in May, however, I would suspect that you had been reexposed and had an additional subsequent immune response.
Unfortunately I don't know if testing companies are even reporting this kind of information. I wish I could be more helpful.
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Thanks for reading, everyone!
See you all next time.
Always,
JS