COVID Transmissions for 5-7-2021
Moderna booster fights variants
Greetings from an undisclosed location in my apartment. Welcome to COVID Transmissions.
It has been 536 days since the first documented human case of COVID-19. The year 536 was declared by historian Michael McCormick to be “the worst year to be alive,” in case you wanted some perspective on living through 2020. That year, there was a massive volcanic eruption that filled the sky with ash, crashed global temperatures, and caused massive crop failures that led to famine in Europe and Asia. Bad deal.
Today we’ll talk about a reason to be optimistic for 2021—Moderna has shown that a booster vaccine dose can work against new variants.
In other news, it’s Friday! Have a great weekend!
As usual, bolded terms are linked to the running newsletter glossary.
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Now, let’s talk COVID.
Moderna reports data on third booster dose covering variants
Good news, everyone! Moderna, which has been working on a third booster dose for their vaccine, targeting new variants of concern, has reported that their booster works:
This is science by press release again, which I don’t love, but here we are. The results are from a Phase 2 trial of the new product, where participants in previous Moderna clinical trials1 were given a third dose of either the original mRNA-1273 vaccine or a modified version that matches the spike protein sequence from the B.1.351 variant that is commonly found in South Africa. This variant was chosen as a target because it is clear that it contains multiple immune-escape mutations, and there is evidence that it can to some degree compromise vaccine effectiveness.
The bottom line here is that there was a robust neutralizing antibody response observed to the new variant with administration of this new vaccine.
I’m lifting this point a bit from Dr. Michael Mina on Twitter, but it’s not actually so obvious that this would be the case. You might expect that this variant vaccine would have worked, because why wouldn’t it? Well, there is a concept called “original antigenic sin.” Neither I nor Dr. Mina gave it that name; it’s an old concept in virology. This concept is best-characterized in immune responses to influenza viruses, which frequently change their surface antigens. Basically, the first influenza virus that a person’s immune system experiences seems to bias the immune response to future influenza viruses. When a new, slightly different influenza virus is experienced, the immune response is dominated by reactivation of memory cells to the original virus. This creates an amount of irrelevant immune response that is unhelpful against the new variant, so the host is not as well protected as they might have been otherwise.
There was some concern that exposure to a previous vaccine might bias the response to a new variant vaccine so that only the older memory response was made. These results demonstrate that this doesn’t happen with the Moderna COVID-19 vaccines, which is great news.
Also in the press release, Moderna mentions that they are working on a “multivalent” vaccine, something I want to call out. A multivalent vaccine targets multiple different agents in one dose. I prefer to use the term to refer to a vaccine that targets different variants or even strains of the same agent (like the seasonal influenza vaccines, which target multiple strains), but sometimes the term is also used to refer to vaccines that target multiple, entirely different pathogens. In this case, though, it refers to a COVID-19 vaccine formulation that targets multiple different variants of the virus.
I’m very interested in this concept, because the study here could establish a precedent that would allow for other manufacturers (like Pfizer) to work on multivalent mRNA vaccines as well. The regulatory pathway for approval that Moderna might follow here could become a blueprint for others to develop similar vaccines. So I would very much like to see how that goes as well.
Anyway, all around, this press release has a lot of good news. In the event that a variant really can escape vaccine-induced immunity, it looks like we can deploy a booster dose to help us reinforce COVID-19 immunity in previously-vaccinated people.
What am I doing to cope with the pandemic? This:
Watching: Letterkenny
Lately I’ve been watching a show called Letterkenny, on which I’m aware I’m very late to the party. It’s a comedy about life in a rural town in Ontario, Canada. Few of you will know this, but I’m a US-Canadian dual citizen, and I’ve been to more than a couple of these sorts of towns. The show is hysterical, though it’s not exactly family-friendly entertainment. Still, it’s cleverly written and clearly by people who appreciate words, culture, and cultural differences. I’m enjoying it a lot.
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No corrections since last issue.
See you all next time.
Always,
JS
This is a good design choice; these patients have a well-monitored history both immediately before, as well as for quite some time after, their vaccination.