Lisa writes:

Just watched Mavis the Structural Maven, TWiV 448.  My goodness what a force.  Thank you for remembering her and introducing her on your last podcast.  What a smart, fun, resilient, and inspirational person.  Wow.  

Thank you for all you do,


Christiane writes:

Hi Kathy,

Just saw this email and thought it might be of interest to the TWiV crowd that has been lamenting the lack of T cells analysis in COVID.

There is now a commercial test to measure SARS-CoV-2 T cells.

Best, Christiane

Earl writes:

Dear TWiV hosts,

Thank you for the interesting, illuminating and useful information you provide.

As a layperson with no background in virology or any of the other sciences most pertinent to the SARS-CoV-2 pandemic, back in March, 2020 I learned a new word: virion.

Since discovering TWiV a month or so later, I have listened to every episode (and watched a few) from the emergence of the new coronavirus to the present. Several weeks after becoming a listener to TWiV I learned of Vincent’s blog and read some of those posts, at least a couple of which (28 July 2004 and 22 July 2010) explained the term virion.

With that in mind, I have been surprised that the word virion is not used more frequently (by hosts and guests) on the podcasts. (I have heard the word used several times on the podcasts, but not as regularly as I expected.) Apart from the word virus itself, the other word that is used most often seems to me to be particle. Sometimes, I think, particle is used to mean virion, but other times it is used to mean a fragment of viral RNA (or DNA), and other times to mean viral antigens.

So, I ask why not use the word virion when that’s what you mean, since it seems to me to be so clear and explicit?

I also thank you for taking the time to define or explain the many words and concepts that probably seem self-evident to all the hosts but which may be new or murky to us lay-listeners. This is particularly useful to me when you delve into biochemistry. Several of the hosts provide this service, and I think that Rich is the leader. I do acknowledge that your audience has grown continuously, and probably some listeners miss some episodes, and it would likely be tedious (even to listeners) and impractical to define/explain every word/concept every time it comes up. But I do very much appreciate the clarity you bring to the virology, immunology, epidemiology, and (with Dr. Daniel Griffin) medicine around the pandemic.



Peoria, Illinois

Suzanne writes:

Texas masking

One problem with dropping the mandates will be for businesses who want to follow the guidelines having to deal with customers angry that we’re not letting them fall back on their “personal responsibility like the governor said.”

It’s easy for Abbott to say businesses can do what they want but he’s not going to be the 18 year old behind the register trying to hold firm against big, loud, selfish fools. 


Stephen writes:

Dear TWiV Team,

On today’s episode you discussed the status of Novavax’s vaccine candidate which is behind Johnson and Johnson despite phase 3 data being (press) released around the same time as J and J. 

The short version is that Novavax’s data was from a non-US (as you noted) trial, that doesn’t match FDA specifications. I know that the number of subjects is low (15,000 compared to the 30,000 in Pfizer and Moderna’s trials and 44,000 for J and J) and I suspect there might be other variations. They are proceeding with a US based phase 3 trial that finished enrollment in February. That said, they’re apparently in talks with FDA to gain authorization based only on the UK trial and Novavax hopes that if that is allowed they could get authorization in early May, but if they have to wait until the US data is available it may take a few months longer (at which point, if President Biden is correct, we’ll have enough doses of other vaccines to cover everyone anyway, so that might impact EUA).



Rafael writes:

Hello all of you from TWiV. 

I’m Rafael, from Belo Horizonte, Brazil and I would like to talk a bit and hear from you guys about my opinion on the 76% number for Manaus in 2020. To me it’s impossible. If you had that it would mean 1.6 million people infected with around 4k deaths at that moment. That would be the lowest Infection Fatality Rate in the world, by far! A lot of the deaths counted as in Manaus were from people that got infected and sick elsewhere and then went to Manaus, since it is pretty much the only city of the state of Amazonas with ICUs or even good hospitals to begin with. And there’s a local law for the epidemic that means that if you die in Manaus, you will be buried there. You can’t transfer the body. Add to that, that the healthcare infrastructure in Manaus is already insufficient, you will get an even higher number of deaths. Manaus has 24 hospitals, but some of those are small facilities, not capable of treating severe cases of anything, really. Reinfections are still very rare. Only 2 are confirmed so far and there are only 20 more under investigation. 

Virology professor Julio Croda, MD, PhD, from Oswaldo Cruz Foundation went to Manaus and he believes that Manaus is yet to reach 50% of prevalence. He also considers that the population affected by this second wave is socially different from the first. In 2020 public hospitals went full capacity first and then the private ones. This time it was the other way around, meaning that now the upper class, that managed to quarantine during the first wave, got infected. Some good old shoe sole epidemiology, I believe.

Here is a link for some of this analysis. It’s in portugues, but I believe that using google translate will be possible to follow it.

But to me, maybe the main flaw is to consider the blood donors. They are not representative at this moment. And as a regular blood donor I can attest that. Imagine you are in an epidemic. Who do you think are the people that are going out and about and end up donating blood? A person that never had covid 19 and is locked inside the house, or a person who already had covid 19 and is less worried of getting it? So to me, a high level of seroprevalence among blood donors is just due to the fact that people exposed to covid will be the ones that are walking around more freely, doing things, including donating blood. Almost all people I know (including me) that are donating are people that had covid before and are more confident to go around places. Of course we know that it’s not 100% safe to walk around even if you already had it, but people still need blood donation (as I needed after an accident) and someone needs to do it. 

I don’t know if I’m right or if it makes sense but I believe that this is one of the very few lines of interpretation of this study.

Thank you all so much for your work and to share it in public platforms. I’ve been following TWiV and related projects from you all since the middle of last year and it has been a fantastic learning experience to me. As I said, I had covid 19 in october/november of last year and I’m glad to be safe and I’m sure that all that I learned from you guys helped me a lot to understand what is going on during these challenging days.



Belo Horizonte – Brazil

John writes:

Dear TWIVers:

A retired M.D. who has been listening since March, a sponsor since late 2020.

It’s great to hear your discussions of the current status of the virus and the literature.

Loved “Dagfin from Oslo’s” version of “Mr. Sandman” and Dickson’s mellifluous rendering so much I added a couple verses, attached herewith:

(The intro “chorus”)


Ms. Labwoman, send a vaccine.

Inject mRNA to start the machine.

My cells will make the spike and make antibodies 

To knock the virus out while I drink hot toddies!*

Get the first jab, a piece of cake,

OK, the second one is harder to take,

But, that’s the neutralizing scene.

Let us knock out Covid 19!

Ms. Labwoman, viruses clone!

I’ll take a shot without a com-plete genome!

Just make an envelope to bring DNA in,

With just enough bases to stop the invasion!

Vi-ro-LO-gists, Vincent, Brianne

& Rich & Dickson &, surely,  A-lan

Keep talking up what’s on the scene!

Let us knock out Covid 19!

*(as I write this, we have 6” of snow and 19 degrees F / -7 C in Cincinnati)
John Sikorski, M.D.
A Smile is Contagious, too! (S. Pastis)

Mark writes:

Dear Vinny and the TWiVs,

Here is a haiku inspired by listener letters to recent episodes thanking TWiV for providing scientific and medical facts.

Facts. Facts. Just the Facts. 

Fight bad opinions and lies.

TWiV spreads just the facts.

As I write this it looks like the New York metro area is getting slammed by another cold front. Would it be cruel and unusual punishment to tell you that days are sunny and temps in the mid 60’s on the Fahrenheit scale here on the California Central Coast? 


Judith writes:

Dear superheroes of TWIV,

Thank you for being such a steady source of information about the pandemic this past year. I have listened to TWIV off and on since my early postdoc days (2009-ish), but your work on SARS-CoV-2 has me hooked, and I haven’t missed an episode since January 2020. This is my first time writing in.

I am just a viral immunologist (like Brianne!) turned stay-at-home-mom. My PhD is in Immunology and Molecular Pathogenesis from Emory University (graduated in 2008), and I did my grad work at the CDC on the role of measles virus accessory proteins P, V, and C. I now live in NYC and have most recently worked at Weill Cornell Medical College on influenza vaccine research using a lentiviral vector system. Before I had my son in 2016, I had migrated over to the writing side of science and was a Medical Writer in an agency for a couple years. When he was born, I took some time off from science to raise him, and now also my daughter, but I have recently gotten back into science through a freelance science writing gig with a great little website called I look forward to the day that my kids are old enough so I can get back to work for real!!

Anyway, down to my question. I’m curious what your thoughts are about the new CDC recommendations regarding what vaccinated people can and can’t do. My internal red flags went off when I read that the CDC now recommends that vaccinated people can be with “low risk” unvaccinated people inside without masks. My thought is mostly directed toward the kids. Isn’t it true that, even though children seem to be at lower risk of severe disease, they are not necessarily much less likely to be infected (and then spread that infection to others they are in contact with, for instance at school)? Furthermore, when they are infected, they can still experience negative outcomes such as multi system inflammatory syndrome (MIS-C) and post-acute sequelae of SARS-CoV-2 infection (PASC). Additionally, there have been a number of reports now on the large percentage of people (I recently read 1 in 3) who experience PASC after recovering from a mild or moderate infection with SARS-CoV-2. So, even low risk isn’t no risk, and outcomes that aren’t death can still be catastrophic for some.

My feeling about this recommendation from the CDC is that it is an effort to not dissuade people from getting vaccinated, but I’m curious about your thoughts. 

Thanks again for your smart and entertaining podcast (don’t change a thing!),

Dr. Mom (aka Judy)

45 degrees F, cloudless and sunny in NYC

Jeanette writes:

I’ve had my two doses of the Pfizer vaccine and I’m so excited and grateful that I’m done, but for some reason I started wondering what would happen if I kept going back for more.  What would happen to your body if you had multiple shots?  Like, if you managed to get two doses of Moderna and two doses of Pfizer and a dose of J&J? Would you get really sick?  Or really healthy? Or turn into a mutant superhero?  Or is it like taking too much vitamin C and your body would flush it out? 



Mona writes:

You were discussing mathematical logs on TwiV 728 with an interjection by Dr. Despommier that they were dead trees, so I was reminded of this joke (told to me by my aunt who did understand logs):

As you know, in the Bible, Noah and his family built a large boat (the Ark) to save the animals from an enormous impending flood.  He took pairs of animals on board to safety so they could multiply when the land reappeared.  After the flood, he found a spot to tie up the ship and release the animals.  But Noah kept track of the animals’ reproductive progress because his sons went out to check.  One time, as they were walking around, they encountered a pair of snakes and said to them, “Why haven’t you multiplied?”   The snakes replied, “We can’t.  We’re adders.”  This was the first year.

The next year, Noah’s sons built some picnic tables using the dead trees lying around so the men could eat their snacks and some lean-tos for shade from the hot sun so they could continue their inventory more comfortably.  And then after a while, they came upon the adders again, but this time, there were baby adders as well.  The sons said to the adders, “Why is it that you adders can multiply?” They answered, “Well, ever since you put in those log tables, …”


Meredith writes:

Dear Twivers,

Long time listener, first time emailer!

My name is Meredith Whitaker, I am currently a medical writer but not too long ago I finished my PhD in Immunology & Microbial Pathogenesis at Weill Cornell Medicine in NYC. My wonderful PhD advisor was Dr Sabine Ehrt, in whose lab I studied two genes of unknown function in Mycobacterium tuberculosis. 

Right now I’m halfway through Episode 728, and the question of ‘why are all the mice female?’ has been raised. I had to pause and write to hazard my educated guess–it may have to do with infecting/housing the animals with their safety in mind. For tuberculosis mouse infections, we use all female mice so that we can group animals together during the aerosolization process and while being housed without having to fear they would fight each other…or eat each other. I’d bet the Twiv T-shirt that I caught during a podcast recording at ASM Microbe 2018 that this is the case here as well!

Thanks for all your great science communication efforts. I actually volunteer with an organization called COVID Act Now running their ‘Research Rundown’ newsletter, in which I frequently link out to the Twix family resources. 

Test negative and stay positive,



Meredith W. Whitaker, PhD

Medical Writer

New York, NY