Hal writes:

First of all, thank you for your excellence.

I am a 64 year old, relatively healthy and fit internal medicine physician practicing in Southern Maine. My second vaccination was on January 20th. Recently, just this week, I contracted the SARS-COV2 virus. This is day five and after nothing more than an annoying cough, mild fever, and a runny nose for a few days, I am almost back to “normal.” Yay! Vaccines work. My question is do I truly need a booster? Fully vaccinated plus COVID, more than likely with the delta variant, in that order. I know there’s no negative outcome in getting the booster, but is there truly a benefit in this scenario? If so, what is it and when would be the best time to get the booster shot?

Thank you, 
Hal J Cohen D.O.

Lamont writes:


What I find interesting there is a documented transmission change of breakthrough infections in fully pfizer vaccinated individuals.

What I sort of expect is this will be abused to continue to argue that the vaccines don’t work with delta.

Jeff writes:

Hi. I was trying to explain the immune system to my 12-year-old son in simple terms. I don’t think that there are really simple terms for the immune system, which is what makes it so fascinating. But anyway, I came up with what I think is a pretty interesting metaphor of musical recordings, and their being played. The idea is that there is a memory (the stored music) which has no specific playing volume, but a spectral analysis would reveal many combined frequencies, each with a relative amplitude. When played, there is an overall amplification that can be set regardless of the recording’s “inscribed” amplitude. This “playing” amplitude expresses all of the memories at their relative amplitudes. Then we talk about immuno-modulation, it is the external, overall, amplitude that we are talking about, and the T/B memory is the spectral decomposition. The T/B memory inscription process is similar to our recording of music — the system records on the “record” a response to what is going on in its environment. Although we don’t usually represent music in terms of its spectral decomposition, there’s no reason that we couldn’t, and if we did, then the T/B immune-memory system would actually work similarly to that way of recording music. Anyway, I’m not sure how far this metaphor or analogy could go, but I thought it was fun at the time. What I wanted to ask you, though, after all this, is what is the best book on the immune system for a 12-year-old … for under $150 (so, like, Janeway is out…although, I could probably get a previous edition cheap! 🙂





Jeff Shrager, PhD
Director of Research, xCures
and Adjunct Professor
Symbolic Systems Program
Stanford University

Johannes writes:

Hi Twivsters,

I’m a little behind in listening, so I am sure someone already told you, but just in case:

In twiv ‘Rats, more Coronaviruses’ from August 29th you were talking about a ligation method that leaves to NO traces and that you didn’t you KNOW of one. 

Gibson assembly would be my obvious example, as I use that in the lab all the time.

All you need for that is fragments that have overlapping sequence of 20 to 30 bp and an enzyme mix containing a 5′ exonuclease that generates long overhangs, a polymerase that fills in the gaps of the annealed single strand regions, and a DNA ligase that seals the nicks of the annealed and filled-in gaps. 

And voila, no traces of ligation because you do not have to use restriction sites if you synthesise or PCR amplify your fragments, and no recombination scars like in gateway cloning.

Have a great day!

Greetings from Perth, Australia.


Adam writes:

Greetings Vincent and everyone,

I love TWIV but I’ve got to take very slight exception to your discussion of Star Trek “red shirts” in TWIV #802; which was in every other respect a terrific episode. 

How many times has it been said on TWIV when discussing statistics “check the denominator”? If we apply that principle to the Star Trek red shirt phenomenon, we get a different story than the usual “narrative” (haha). While it is true that more red shirts (engineering, communications, and security personnel) died  in the three seasons of Star Trek, than either gold shirts (command positions), or blue shirts (science/medical staff), if we look at the population of  the Enterprise we see something else. 

By the way. I have heard rumors that there were some Star Trek shows after the original series, but I suspect that might be fake news. 

Anyway, by raw numbers the deaths break down as

red shirt – 25 (58% of total deaths)
gold shirt – 10 (23% of total deaths)
blue shirt – 8. (19% of total deaths)

The Star Trek Enterprise technical manual states that there were 239 red shirts on the Enterprise, 55 gold shirts, and 136 blue shirts. That means the death rate by shirt color is

Red shirt = 25/239 = roughly 10%
Gold shirt = 10/55 == roughly 18%
Blue shirt = 8/136 = roughly 6%

That means the safest position, statistically, is to be a blue shirt science officer. Next is to be a red shirt engineer/ security person, and the riskiest position or highest death rate is with the gold shirt command officers. 

Credit for this calculation is not mine, but goes to mathematician James Grimes whom some of you may know from Numberphile or Singing Banana. 

Keep up the great work. I love TWIV and all of the microbe tv offerings.

Thanks for all of the knowledge and entertainment. 



Georgia writes:

Hi Vincent and crew, 

Listening to Shane Crotty’s responses to your questions and impact of timing of boosters, I wondered if I might apply that to my situation with the shingles vaccine.

I got the first Shingrix shot at the end of August.  The timing for the second shot is identified as two to six months.  Based on the discussion in the above episode, do you think it might be better to get the second Shingrix injection towards the later time frame?  Is it fair to extrapolate response to Covid-19 vaccinations to the Shingrix vaccine as far as timing for the boost is concerned?

Some background, I developed shingles of the trigeminal ganglia on the maxillary branch (V2) early in July.  After I finished a ten day course of acyclovir (800 mg, 5 x a day)  the shingles resurged and expanded to include the ophthalmic branch (V1) and I took another course of acyclovir and my eye doctor put me on a 90 day course of 1,000 mg Valacyclovir as soon as I finished the acyclovir.  I read up at the CDC on Shingrix and confirmed the use of antivirals wouldn’t interfere with getting the vaccination.

Alas, I was left with some nerve damage but I haven’t given up on the hope that it might eventually improve.  

Love all the microbe.tv shows and listen faithfully.  


Christos writes:


I love your show. Keep communicating science, you are very unique in what you ‘re doing.

I want to hear your opinion on the use of TCID50 to determine virus titers either with in vitro assays or in patients. I keep seeing it on SARS-2 papers and to be honest I hate it. I feel like quantification of infectious particles should be measured only in PFUs. TCID50 mixes up CPE, general pathogenic effects, syncytia and so forth. It doesn’t seem right for viruses like SARS-2. Am I wrong?

Here’s a neat little paper describing 2 mink outbreaks https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1009883#sec012 



Bev writes:

You’ll probably have lots of people telling you this but just in case ……

Dogs’ eyes refresh at a faster rate than ours do so what we see as a moving screen is a flickering mess. 

Here’s the first link I found on it https://pets.thenest.com/dogs-see-tv-same-humans-11481.html 

Peace, Bev

Kathryn writes:

Dear TWIV,

   I was interested in Dixon’s comment about the most recent IPCC report. I’d like to recommend Project Drawdown (https://www.drawdown.org/solutions/table-of-solutions plus the book https://www.drawdown.org/the-book) which is a great resource. It ranks various climate solutions by impact to help understand the most important things to do to help stop climate change. It makes you feel better to work on solutions.


   Kathryn, just an energy efficiency engineer

Charles writes:

Ave twivumvirs, those who are about to plaque salute you.

I must confess that I am quite far behind on TWiV. Aside from the few I have attended in person at ASV meetings, I only started listening in earnest a few years ago. Currently, a vast gulf of time separates us as I work my way through your extensive archive. Your broadcast started around the same time that my adult career as a virologist began as a graduate student at Colorado State University. It has been fascinating to follow the virological highlights of the past ten years as my career has progressed along with your program. Thank you for documenting the weather, including your experience during Hurricane Sandy, which welcomed me to my post-doc in the laboratory of Dr. Eckard Wimmer.

I am not sure if this has come up, but for my listener pick of the week I would like to suggest Arrowsmith by Sinclair Lewis. As phage therapy comes back into the limelight, it is important to recognize that this idea is over a century old and even reached public consciousness in this early 20th century novel about a microbiology graduate student and his irascible German professor. I would also recommend another book from the 1920s called Microbe Hunters written by Paul de Kruif. These books were highly influential during my childhood and influenced my decision to become a virologist.


Dr. Charles “Brandon” Stauft, Ph.D.