Lisa and David write:

Vincent, Alan, Dickson, and Brianne:

We have spent the past week working toward COVID-19 mitigation strategies in our community, and I just flipped on Sunday’s TWiV (today is Wednesday). Not surprisingly, Tennessee was one of your topics. You’ll be glad to know that your opinions are respected and shared by the professionals in our county.

Tennessee has an interesting state health department reach: while smaller counties follow the direction of the state, counties including Hamilton (where we live in Chattanooga) can follow the directives of the local health department. The Chattanooga/Hamilton County health department is proudly continuing to advise childhood vaccination and vaccination against COVID-19 and has had two such events in the past week.

As far as our strategies go, we continue to advise the county mayor and schools, plus Purdue University and our other schools and businesses, and are taking the Delta variant seriously. 100% of sequencing done locally is the Delta variant, and hospitalizations are following the same curve as Springfield right now.

Thanks for continuing to educate us all–without you, we couldn’t do our job. As always, we believe it can be done: school, work, you name it, and vaccination along with basic mitigation is our strategy.

Your friends in Chattanooga,

Lisa Smith and David Bruce

Rebecca writes:

Speaking of Pilots being supremely calm I have a little story. I remember years ago hearing the recording of a pilot who was watching another plane have a disaster in the air. The plane was obviously going to crash and the pilot described it as calmly as if he were placing an order at Starbucks.

Remembering that actually makes me feel better when I’m on a plane … that my pilot won’t freak out if something goes wrong!

Rebecca from Pittsburgh

Pete writes:


I have been listening for about 5 years, but there has never been a better episode than 773.

Everything Laurie said was spot on. I should not have been surprised that you gave her a platform: you can lose me in jargon, but you cannot fool me.  You are the real science deal.

Many thanks, Pete

Ryan writes:


I’m writing from Silver Spring, MD where it’s 28 degrees C and I’m impatiently waiting to start my junior year studying cell biology & genetics at UMD College Park.

In TWIV 777, you read a letter about the negative comments on the CDC covid posts on facebook, and frankly, your incredulous reactions to the false claims were kind of adorable! You really are just a bit naive to the level of madness that exists out there, aren’t you? 

Well, I’m familiar with those CDC posts and such, and I have had the fortunate experience of talking to a cousin who’s been exposed to this misinformation. He happens to be sharp enough to listen and understand, but the information he’s been exposed to is awful. The conversation was illuminating for both of us, and I thought I’d share some of the common myths with you guys:

– “The mRNA vaccines aren’t actually vaccines.” This is one I’ve seen a lot, and it confused the hell out of me. According to my cousin, he was told that all vaccines must contain the actual pathogen – either inactivated or attenuated. This myth was easy to dispel by explaining subunit, viral vectors, etc . . . I didn’t have to bring up mRNA vaccines. 

– “The inventor of PCR says that it shouldn’t be used to detect Covid.” That’s a weird one, huh? But I’ve seen it before. I guess people are claiming that it’s not a diagnostic tool? I don’t know the origin of that claim, but I explained what a ubiquitous tool PCR is and how long it’s been around. 

– “PCR is just a copy machine, so you can find anything.” Another strange thing that’s floating around. This is harder to dispel, because you have to find a person willing to listen to a summary of how PCR works. I’ve also seen people online misunderstand what Ct values are and claim that – actual quote – experts “play games” with them to manipulate results.

– “mRNA vaccines are gene therapy.” Probably the most common one. In fact, my cousin specifically heard that they modify mitochondrial DNA. Another difficult myth to dispel because, even though it’s pretty basic, it’s still cell biology. Distrust and/or impatience halts discussion of anything remotely technical. 

I thought you may find some of that interesting. It’s often the case that people will encounter snippets of scientific facts or terminology and be unable to contextualize them, giving rise to myths. But finding those willing to learn the context is rare. Too bad they don’t listen to TWIV.


Ryan R. 

Michael writes:

Dear Professor Racaniello:

So the other day I asked my Fire TV to take me to your YouTube channel, but Amazon’s speech analytics could not parse “Racaniello”. You can probably guess what Amazon came up with from the attached. Anyway, I thought it might be a fun little mascot/avatar.


Vincent Raccoon Yellow

AL writes:

Dear Vincent and TWiV team,

Long time listener, first time writer! Thank you for your sanity and science over the past year and a half; I don’t know how I would have made it through this far without TWiV, and keeping up with your updates and myth debunking have helped me combat misinformation and misunderstandings in my own circles. 

I’m writing to share a recent bright spot for me. I live in Japan, where the vaccination rollout has been unnecessarily slow, and a media focus on reactogenicity over effectiveness has further fueled hesitancy in some demographics. However, I was pleased to see that my local government’s newsletter to residents (distributed free of charge in every mailbox) was factual, balanced, and did a great job of addressing concerns in a reassuring manner.  I am attaching a photo of the back page of the newsletter, which gently takes aim at the biggest worries, complete with cute graphics and accurate but accessible phrasing. 

The main clipboard graphic is titled “About the SARS-CoV-2 vaccine”

The left column addresses reactogenicity (which is the term they used! Not “side effects!”) It spells out what might happen, that the second shot often hits harder, and notes that almost all recipients are back to their usual selves in a day or two. It does also list when to call to get medical advice (fever persisting more than two days, extreme symptoms, etc.) and lists a 24-hour phone line to contact to report anything unusual. 

The right column defines and explains anaphylactic reactions but makes clear they are rare, can be treated immediately, and that there are medical personnel standing by after each jab just in case. At the bottom of the column, it even explains the vaccine’s 95% effectiveness rate, going so far as to clarify that it does NOT mean it works in only 95% of people. 

The tan box below is a letter from a respected professor at a major medical school in the area and member of the government’s taskforce on preventing the spread of SARS-CoV-2. He writes in a friendly and professional manner about the great concerted effort made to create these vaccines, their effectiveness, how the benefits far outweigh the risks of reactogenicity, and why the reactogenicity is in fact a good sign that your immune system is doing what it should. He urges people to get vaccinated for the benefit of society and a return to normal, then finishes by singing the praises of this new, highly effective vaccine type (though he does not specifically mention mRNA.) The QR code is a link to a video version of his statement for greater accessibility. 

After all my complaining about how so many governments have handled things poorly, I was happy to see the local offices in Ōta Ward, Tokyo doing well and wanted to share a little positivity. 

Thanks again for everything and keep up the good work!


Charles writes:

Hello TWiVers;

91F, 33C, 55% relative humidity in Chapel Hill, in other words, hot and sticky, but tolerable when compared to Dr. Condit’s haunts, past and present.

Now that we know more about the fitness of the delta and beta variants of SARS-CoV-2, I would like to revisit my position on extending the time between doses for the two shot vaccines.  I had sided with the United Kingdom and others.  That put me at odds with the TWiVers, Dr. Fauci and most importantly, with my life partner.  That was not a comfortable place to be.

I am going to defend myself a bit.  Times have changed.  When the vaccines first got Emergency Use Authorization, there were many arms in search of a vaccine.  Which is very different from now.  Next, the Moderna vaccine and by extension the Pfizer-BioNTech (*1) vaccine had great protection (92.1%) two weeks after the first shot (*2).  Not too far from the 94.5% two weeks after the second shot.  I felt better about my position just a few weeks ago when TWiV reviewed the paper: “Extended interval BNT162b2 vaccination enhances peak antibody generation in older people”(*3).  For a good, at least from this lay person’s point of view, case for a delayed second dose see the statement from the BC Centre for Disease Control (*4).

OK, that was then and this is now.  Instead of arms looking for vaccine doses, we now have vaccine doses looking for arms.  Instead of 92.1% vs 94.5% effective vaccines for one vs two doses, we now have 33% vs 88% (*5).  I am a hard headed IT guy, but when circumstances change or we have better data, I am willing to change my mind.  It looks like the Brits are changing their mind as well, going from 12 to 8 weeks (*6).  I will go beyond the Brits and say stick to the schedule from the phase III studies.  Where have I heard that before?

One thing I have not changed my mind about, is that for the next pandemic, we need better data about one vs two vaccine doses and what is the best delay.  I think the best way to get the needed data and have very fast vaccine development is to have more centralized data monitoring committees and use pooled, time matched control groups.

I probably should not point this out, I did not admit I was wrong, even in hindsight.  At the time I think both ideas had merit.  The epidemiologists will be pouring over the data from the COVID-19 pandemic for decades.  I hope we have a better idea of what to do next time.

I may not agree with you 100% of the time, but I always find your logic to be excellent and your knowledge to be extremely valuable.  Long live the long form scientific podcasts, complete with their diversions to stump grinders, snow shovels, manual transmissions and pet health updates.

Again thanks,


*1) From Dr. Daniel Griffin while on TWiV.  Dr. Griffin probably said it more elegantly than I am, but here goes from memory: The differences between the Moderna and the Pfizer/BioNTech vaccines are the same as the differences between Coke in a can and Coke in a bottle.


Table 15, line 3.

*3) TWiV link:

Direct link to the paper:




Lori writes:

Hello to my favourite Podcasters, 

I have been listening to past Immune and TWiV episodes and have a few questions.

1. Immune episode 16, B is for Bursa, a paper on Marek’s disease in chickens caused by herpesvirus is discussed.  Vaccines are given to chickens yet still 1-2 % of the birds will die from infection.   The vaccine does not provide sterilizing immunity.  A comment is made that most vaccines DO provide sterilizing immunity but from  listening to more recent TWiV and Immune episodes I believe that that statement no longer holds, that actually most vaccines DO NOT provide sterilizing immunity,  am I wrong?   Can you name some of the vaccines  that do provide sterilizing immunity?  

2.  TWiV episode 217, I just flu in and my arms are shot 😂,from January 2013. In this episode what causes the seasonality of the flu virus was brought up and how little is understood about it. With our experience over the past year and a half the thought immediately came into my head that human behaviour is probably the biggest influence on the seasonality of the flu. What do you think? 

3.  Do you think   mRNA vaccine advances will help lead to a universal flu vaccine  or will the constant variant change of influenza continue to be an issue?

Best Regards,


Blue Pilgrim writes:

Over 1,200 doctors and scientists condemn UK COVID-19 policy as “dangerous and unethical”

Thomas Scripps

13 hours ago

More than 1,200 scientists and doctors have signed the open letter to The Lancet medical journal of July 7 opposing the UK government’s plan for mass infection as a “dangerous and unethical experiment.”

Just over 120 experts had signed the letter when it was first published. A week later, that number has increased tenfold.

April writes:

Hi TWIV team,

Thankfully the smoke has cleared and it’s 28C at 9:30m pm. I was listening to “this week in aviation”. HA! I have more cool aviation picks. It’s my friends at the local GA airport, Felts Field (SFF). Addison Pemberton and his family and friends have restored 16+ airplanes over the past 20-ish years.

Thanks for all the good info and fun,