Sam writes:


I am writing seeking advice to address many of the vaccine concerns I have heard. I work as a nurse in an intensive care unit and my hospital has recently announced they will mandate vaccination to maintain employment within the hospital. I personally fully support this decision, but I have many coworkers that are very against it despite taking care of COVID-19 patients first hand. I have had many people come to me seeking my opinion about why they should get vaccination, as I have been very involved in the vaccination clinics for the community and am the only nurse with a microbiology background. I was wondering if you had any input on how to address the most common question of “Why should I get the vaccine if vaccinated healthcare workers are still getting the virus/shedding virus?”

Typically my answer to vaccination has been “It is your ethical responsibility as a healthcare worker to protect the vulnerable population you work with”. However, in this case if there is data showing you are possibly shedding virus (like this new paper from the CDC resulting in a change in guidelines), how do you respond? I have been saying that at least in other variants studies have shown a decrease in viral load (thinking of the papers in Israel you talked about early on in the vaccination process), so you should shed less virus depending on what strain you pick up and prepare for the booster to come as things develop. I’m wondering if you have a better answer that might help address this concern. Many people feel that despite being a healthcare worker, vaccination is a personal choice and they are only risking their own life. 

Thank you,


Christina writes:

Good afternoon, TWiV team,

In suburban Dallas, where I live, it is currently 89F/32C with 52% humidity. This is stunningly mild weather for Texas in August.

Thank you for all the information you provide and your efforts to define terms and phenomena for listeners like me who are not scientists or healthcare providers. My husband still chuckles when I say, “The plural of ‘anecdote’ is not ‘data.'”

This time I am the one with a little extra information, specifically pertaining to Bistra’s letter, read on episode 788. He is a good friend who seeks out accurate information to support his friends’ decision-making. (Full disclosure: I am not a doctor, nor do I play one on TV. The comments following are in no way intended as a substitute for professional medical advice.) That said, I have lived with autoimmune disease for 21 years. Over that time, I have learned the value of educating myself on my diagnoses and medications in an effort to become the best expert I can possibly be on my own health. Listening to TWiV is currently part of that. So has lurking about the website of the American College of Rheumatology, the major US professional organization for the kind of specialists who treat most autoimmune diseases.

Among other things, their website ( includes access to recordings of Town Hall webinars on topics related to COVID-19 and autoimmune disease, the Vaccine Clinical Guidance Summary developed by the ACR task force, and a patient resource document with an abundance of helpful links they have vetted for accuracy. Here is the link to that patient-focused document, in the hope that it will help Bistra provide accurate information to his friends in Bulgaria:

Spoiler alert: the official stance of the American College of Rheumatologists is very much in favor of vaccination, although they acknowledge the decision ultimately belongs to the patient and physician. They do suggest tips on the timing of vaccination relative to certain medications that may help maximize immune response.

Many of the links on that patient resource document lead to the patient-focused website Interested parties can register for this site’s COVID-19 support email updates, which I have found very helpful in providing pandemic information specifically tailored to those with autoimmune diseases and their caregivers.

All of that probably counts as a listener pick, but I have one more if time permits or you need one for a future episode. This pick dovetails with Alan’s earlier Librivox pick and Brianne’s pick of the article about scientists needing to read more fiction. provides “annotated audiobooks,” which really boils down to a sort of virtual audio bookclub delivered via weekly podcast. The podcast host, Heather Ordover, chooses classic fiction in the public domain (mostly from Librivox recordings) and invests many hours of research behind the scenes on tricky vocabulary, author background, and cultural references we no longer understand. Each episode consists of some crafty or creative talk up front and one or two chapters of the current book with helpful commentary by Heather before and after. In the 14 years of this podcast, listeners like me have experienced books ranging from Little Women and Anne of Green Gables to The Count of Monte Cristo and Frankenstein to Jane Eyre and Sense and Sensibility. Heather is the English teacher we all wish we had, but her most recent job was not teaching literature but training contact tracers for her state’s pandemic response. In fact, she is the one who alerted me to TWiV, so it seems only fitting that I suggest Heather and CraftLit as a listener pick. As she likes to say, “If your hands are too busy to pick up a book, at least you can turn one on.”

Thanks again for all you do to help listeners understand the real facts and data behind the headlines and misinformation.



David writes:

It is currently 68 degrees here in Redmond, WA, which doesn’t sound too bad, but that’s because it’s nearly 3 in the morning, and it’s expected that we’ll be near or above 100 at the highs for the next couple days. That’s in fact the main reason I’m asking this question. For context, where I am we have 81.9% of the eligible population started vaccination, and 76% complete, and all of my immediate family and I are fully vaccinated. The recommendation in my county currently is that fully vaccinated people should ‘consider’ wearing a mask in public indoor areas. The issue at this specific juncture is that I sweat bullets in 100 degree heat even without a mask trapping all the heat and humidity of my breath to my face.

To be clear, I’m not at all anti-mask, and I wear mine without complaint in scenarios where it is mandated, but in other scenarios where I am only supposed to ‘consider’ masking, I admit I have a hard time coming up with reasons why I should make myself even more hot and uncomfortable. In those scenarios, I rarely am in prolonged close contact with anyone, and in those rare circumstances where I am, it’s with other people who I know are also fully vaccinated. My understanding is that the evidence for easier transmission from vaccinated people for the delta variant compared to other variants is inconclusive at most e.g. the Singapore paper you’ve talked about recently. And while yes I could be infected even after vaccination, my understanding is that the mask isn’t offering me that much additional protection from some hypothetical droplet somehow floating in the air for the medium to long term that contains SARS-CoV-2 anyway (which I understand to be considered a pretty low risk scenario). And as I am fully vaccinated, the chances of infection if I do run into this hypothetical droplet are low, and even if it did happen the chance of serious symptoms, hospitalization, or death are way lower still (the way I’ve been thinking about is that for a fully vaccinated individual, it doesn’t seem that much more dangerous than the dangers of any other respiratory illness, and I never wore a mask before to stop the common cold or the flu. If that’s a mistaken thought, please correct it). There’s rarely even any unvaccinated person within eyesight to whom my masking could exert social pressure for them to mask.

I’d have no issue making myself more miserable from the heat in those scenarios if I knew there was good reasons that doing so was more than hygiene theater, but as it stands when I ‘consider’ the question I struggle to come up with any, and would appreciate any input any of you would have on this question.



Amelia writes:

Hello TWiV!

The latest argument I’ve heard from some antivax friends & family is that vaccination causes the virus to evolve into a more virulent form. Of course, this is coming mostly from people who don’t believe in evolution anyway, so I don’t think they are arguing in good faith here.

But they did share a journal article: Read AF, Baigent SJ, Powers C, Kgosana LB, Blackwell L, Smith LP, et al. (2015) Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens. PLoS Biol 13(7): e1002198. 

In this work, they show that leaky vaccines result in increased virulence among the unvaccinated using chickens and Marek’s disease virus. It’s commonly reported in the news, especially “news” consumed by anti-vaxxers, that the sars-cov-2 vaccines do not prevent vaccinated people from getting infected and transmitting the virus to others.

The authors also claim that most human vaccines are sterilizing. In discussions about the sars-cov-2 vaccines, I’ve heard claims that it is remarkable that they do reduce infection and transmission.

1) Are human vaccines usually able to prevent infection and transmission, as well as disease? 

2) What is the potential for the current sars-cov-2 vaccines to “enhance the transmission of highly virulent pathogens”? 

3) Is this issue considered when a new vaccine is developed and released?

Of course, in the end, one solution is to just get vaccinated if you can. I’m still impatiently waiting for vaccine authorization for my toddler, and encouraging everyone I know to get vaccinated.

Thank you for keeping us informed,



Amelia Nestler, PhD
Scappoose, OR

Ronald writes:
hi twiv team:

thanks for all you do to make virology accessible to those of us who never contemplated it when coming up but are fascinated by it now.

we’re FINALLY seeing articles that educate the public about the full story of the immune system. this is what you’ve been preaching for months, the highlight (for me) being TWIV 736 with alessandro sette. i think the comic in this story is great.

as an aside: i think science journalism needs to have a navel-gazing moment (alan, please go kick some butt) to understand why it takes them 6+ months to use proper terminology (strain vs variant) or, more importantly, to tell the full story about a thing, e.g. that initial antibodies are the NOT the only defense (ala b & t cells). or that vaccines are primarily about reducing disease not infection, therefore infection post-vaccine is normal. (i’m still looking for mainstream article about the later.)

all the best.


ronald s chong, phd.

(phd from univ of michigan computer science/cognitive psych, 1998)

go blue! (for kathy 🙂)

Agnes writes:


I’ve been an avid TWiV listener for almost two years now, and I just wanted to send a link to a series of space shuttle prints (Challenger, Discovery, Atlantis etc) by Kevin Dart,  that I think might be of interest to both prof.Racaniello and prof. Condit and possibly the rest of TwiV’s team.

Thanks for all that you do!



P.S. It is currently a hot and sunny 27’C in Toronto, Ontario