COVID Transmissions for 8-20-2021

Boosters and barriers

Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions.

It has been 640 days since the first documented human case of COVID-19. While I normally pick a year to discuss, 640 happens to be record for the number of people ever transported on a Boeing C-17 military aircraft. That record was set this week, during the evacuation of Kabul, when the US military fit that many Afghan refugees onto one of these aircraft: https://www.defenseone.com/policy/2021/08/inside-reach-871-us-c-17-packed-640-people-trying-escape-taliban/184563/

I hope that the US can continue to evacuate Afghan refugees fleeing the Taliban in the midst of this pandemic. The world is full of trouble right now, and I hope that we can navigate it.

Today, we’ll discuss the prospect of additional booster doses and also the usefulness of plastic barriers as a means to control infection risk in indoor spaces. Then, we’ll take a break for the weekend—please try to enjoy it.

Bolded terms are linked to the running newsletter glossary.

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Now, let’s talk COVID.

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US calls for booster doses for people who were mRNA-vaccinated >8 months ago

The US is moving to encourage booster doses for people who got mRNA vaccines more than 8 months ago: https://www.reuters.com/world/us/us-start-offering-covid-19-vaccine-booster-doses-september-2021-08-18/

As the article explains, officials also anticipate that people who received the J&J vaccine will eventually require booster doses, but that vaccine has not been available for 8 months at this time.

Before I go on, I want to say something: if the recommendation from the CDC is to get a booster dose, I am going to get one when it is my turn, provided there is enough vaccination capacity for me to do so. While I may not think this is the optimal strategy, vaccination strategies work best when everyone is on the same page. I’m not going to be a rebel, even if I have my doubts about this particular issue.

I have been openly skeptical about the need for booster doses in the past, and the World Health Organization has also recommended against them. The US government claims that there is evidence supporting a need for booster doses, but I do not believe that the evidence they cite is sufficient to change the preferred strategy.

Numerous other scientists have also questioned the evidentiary support for this approach, though admittedly this position is not monolithic in the scientific community: https://www.reuters.com/business/healthcare-pharmaceuticals/scientists-question-evidence-behind-us-covid-19-booster-shot-drive-2021-08-19/

I don’t think opinion is the best way to look at these things, however. Let’s turn to the evidence. The government has pointed to three studies to justify the decision to recommend COVID-19 vaccine boosters:

1. A study showing that with the emergence of the Delta variant, vaccine effectiveness among nursing home residents dropped from ~74% to ~53%: https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e3.htm?s_cid=mm7034e3_w

2. A study showing that vaccine effectiveness in New York fell from ~91% to ~80% with the emergence of the Delta variant: https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e1.htm?s_cid=mm7034e1_w

3. Another study suggesting that vaccine effectiveness against hospitalization remains high: https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e2.htm?s_cid=mm7034e2_w

According to epidemiologist Ellie Murray, quoted in The New York Times, these studies, taken together, suggest the following:

Together, the new studies indicate overall that vaccines have an effectiveness of roughly 55 percent against all infections, 80 percent against symptomatic infection, and 90 percent or higher against hospitalization, noted Ellie Murray, an epidemiologist at Boston University.

I’m not sure exactly how Dr. Murray got to this conclusion, but she has consistently been one of the voices I trust throughout the pandemic. However, if her analysis is correct, I don’t understand why we are pushing for booster vaccination.

I do not put much stock in the numbers about prevention of all infections, because infections without symptoms are the entire point of vaccination. We need to remember what we developed these vaccines to do—prevent disease. While preventing infection also means preventing transmission, getting infected without symptoms does not necessarily mean a vaccinated person can transmit disease, either. So, I don’t think that we should rest all of our policy on that 55% number.

When we look at effectiveness against disease, the numbers appear to confirm what I suspected last time I wrote about this—that booster vaccination offers us something like a 10-20% potential protection against symptomatic disease. I come to this number by assuming that the best a booster can do is change 80% into 100%, and will probably be more likely to make it 90%. Against hospitalization, it seems to offer even less potential upside.

I also have to admit that I am not terribly surprised to see vaccine effectiveness in the real world dropping by marginal amounts. Most vaccines see some drop in effectiveness over time, but it isn’t always a race to the bottom. Sometimes a drop in effectiveness bottoms out and stays stable. Sometimes it is reflective of changes in behavior among vaccinated people, too. Remember that when the vaccine trials were first conducted, universal masking was recommended. Social distancing procedures were commonplace. Many businesses were still closed. People who enrolled in trials were ones who were concerned enough about COVID-19 to be willing to be part of an experiment, and I bet they followed the rules about protecting themselves. Vaccine efficacy as seen in the trial was, in my opinion, bound to be higher than real-world vaccine effectiveness as restrictions were relaxed. It seems likely to me that at least some of the drop seen in these studies reflects those differences, further eating into the potential benefits of a booster dose at a societal and an individual level.

Meanwhile, there are still hundreds of millions of Americans—and billions of people around the world—who could be protected as high as 80-90% by being vaccinated for the very first time. We have a limited number of vaccine doses in the world, and we have a limited number of people who can put those doses into patients. With many large vaccination centers now closed, is it logistically a good idea to focus on additional doses for vaccinated people on top of trying to increase overall vaccination rates?

Now, realistically, more people have to want to get the vaccine, but vaccination numbers in the US are rising as more mandates have been imposed and as the Delta variant has caused a case surge. It is hard for me to feel confident that we should ask 190 million people to rush back to clinics over the next 8 months to get third doses of vaccine. With lowered capacity for vaccination, and likelihood that tens of millions of children under 12 will soon be approved to receive their own vaccines, I really wonder what this is going to do for our ability to reliably meet demand and vaccinate new patients.

And then there’s the rest of the world to consider, where around 5 billion people remain unvaccinated. It just strikes me that it would be better to get everyone up to even a slightly lower baseline level of protection than to repurpose healthcare capacity for the purpose of boosters.

On the other hand, I am not the CDC and I am not the surgeon general. I don’t have all the information that they have, and I’m not the one calling the shots. There is an alternative view here, where these booster doses could substantially help curtail transmission of a surging Delta variant, in people who we can already rely on to get the vaccine. There’s an argument to be made here, and it’s one that is going to be best made with data. I am interested in hearing more. where I currently stand, if offered the choice, I would rather vaccinate a new patient than administer a booster, but I admit that I could be wrong. It would hardly be the first time that’s happened. It’s important that as a scientist, I remain open to new answers to questions when the information changes. There is not some magic book of science somewhere that has all the answers. There is just the facts that we can learn from studying the world, and those are always subject to change as new realities emerge.

Do plastic barriers do anything?

A recent article in The New York Times covers something that I think about a lot but hasn’t yet made it into the newsletter—the topic of plastic barriers as a preventive measure for COVID-19: https://www.nytimes.com/2021/08/19/well/live/coronavirus-restaurants-classrooms-salons.html

The article goes into great detail about this (and is worth reading), but we can convince ourselves that these barriers are not helpful in a pretty simple way. There are two notable ways to catch COVID-19—through large droplets and through aerosols. SARS-CoV-2 can communicate through both, it is thought, but it does seem that most people catch it through aerosol transmission.

Large droplets follow ballistic trajectories when they are expelled; when someone coughs or sneezes them out, they’re almost like birdshot from a gun, traveling a little distance and then coming to rest. Nothing keeps them aloft because they are too heavy. When they get onto a person, they can be smeared around and eventually find their way into a permissive structure, like the nose, mouth, or eyes, and infection can be initiated there. In a world of infectious disease dominated by these large droplets, a plastic barrier makes a kind of sense. Large droplets can deposit on surfaces, and they don’t get up and walk away.

Aerosols are a different matter. These particles are light enough that they can stay aloft and even move up and down spatially. They behave more like a gas than like a shotgun blast. These particles can flow around plastic barriers, and the best way to stop them is to get them out of the air. Several options are suitable for this: for one, airflow. Remember my emphasis in past issues that ventilation is one of the five key strategies to prevent and control COVID-19. Another option is to eliminate these aerosols from the air—by absorbing or filtering them. HEPA filters in a good ventilation system can do this. Masks can also do this—either by absorbing aerosols right as they are exhaled, or absorbing them as a person inhales.

The article linked also points out that barriers can disrupt the flow of air in a room, potentially creating dead zones where air does not move at all. That could potentially make the risk of COVID-19 higher in places where these barriers are used, since they could concentrate infectious aerosols. That seems less definitive, but I do feel confident saying that I think these barriers are theatrical and not practical. What will serve everyone better is to mask up, be in well-ventilated places, and get vaccinated.

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What am I doing to cope with the pandemic? This:

Re-watching: The Legend of Korra

The animated Avatar franchise, which began with Avatar: The Last Airbender, is really one of the best achievements in modern animated television. It tells stories that are relatable for all ages and that have something to say about the human condition.

Lately, I’ve been quite busy, and so I haven’t really felt like I can dedicate much energy to new entertainment. Having something I’ve already seen going in the background while I work on, say, a newsletter, can be a nice thing. It isn’t too demanding on my mental energy.

The Legend of Korra is the second entry of two in the franchise. It tracks a teenage Avatar, a master of elemental forces, as she comes into her power and wisdom. It’s a fun ride, though perhaps a bit more uneven in its quality than the original series.

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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