Lori writes:

Hello Again, 

I wrote to you yesterday but just have to add that today I listened to your interview with Julius S Younger (episode 373).  WOW, love it, I laughed and cried.  Who would have thought a science podcast would cause such emotion.  What an interesting life, he died the year after this interview, so glad we have this record.

Thank you once again.


Anthony writes:

And Post Polio now?



Mary writes:

Hello good people of TWiV,

Sweden is not recommending that children 5-11 be vaccinated according to the linked article below. They say the benefits do not outweigh the risks. Are the risks really greater when vaccinating this age group? I thought the data show the opposite. I’d like to hear the panel’s take on this as this concerns me because my twin 7 year olds have already received their first dose and due for the second one next week.

Your podcast has been my number one go-to for all things related to SARS-CoV-2. Thank you for your service!


Brooklin Ontario Canada


Kevin writes:

Dear TWiV crew,

I’ve been enjoying the recent TWiVs, and, as of late, you seem to be hammering the message that RNA load from RT-PCR does not correlate well with infectious viral titer.  In other words, that RT-PCR CT value is not a good proxy for the level of infectiousness.

While I now agree with those statements, I have to admit I was quite surprised when presented with the data that support them: specifically, in Figure 2 in the Puhach et al. preprint, there is a statistically significant trend, yet a very very poor correlation between RNA genome copies/mL and FFU/mL.

Many previous studies rely on the false premise that “RNA load is proportional to infectious viral titer.”  But, since that premise is incorrect, the conclusions they make may be in error.

For example, you all have said this is one reason why the Provincetown study is flawed (the study that showed similar CT values between delta-infected vaccinated and unvaccinated people and jumped to the conclusion that they transmit at equal rates).

I’m curious, then, on your opinions regarding other studies that rely on this same false premise. Namely:

1) The “University of Colorado study” that suggested 2% of people carry 90% of SARS-CoV-2 (quantified by RNA viral load).

2) The “Singapore study” that suggested vaccinated people clear virus faster than unvaccinated people (quantified by RNA viral load).

3) The contentious “pre-pandemic EcoHealth Alliance study” that, many people argue, was gain-of-function by showing WIV-1 chimeras replicate faster (again, according to the false premise that increased RNA load is proportional to increased infectious viral titers). (This is not to mention the other flaw in the argument that this work demonstrates GOF— there is not a t = 0 time-point for the RNA load kinetics).  See this article for the most pertinent figures from the EcoHealth Alliance Report to the NIH and Vincent’s quote that this is “no question gain of function” (perhaps he has a different opinion now?). https://theintercept.com/2021/09/09/covid-origins-gain-of-function-research/ 

I could go on and list more studies that rely on this false premise for their conclusions. But, I guess my greater interest is hearing your opinions on when we should and should not dismiss conclusions that rely on it.  Do we dismiss them before translating their conclusions to public health policy?  Do we give them the benefit of the doubt in the midst of a pandemic?  Do we dismiss the conclusions as paradigms for virology but err on the side of caution for public health?  How much of virology has relied on this (sometimes) false premise?

Thank you for reading this, and thank you for continuing to explain all of pandemic’s nuances to me.

Best wishes,


From Wisconsin, where it is snowy and -12 degrees Fahrenheit

Richard writes:

For Dickson

The Associated Press (@AP) Tweeted:

Walmart said it has taken a stake in agriculture startup Plenty, becoming the first large U.S. retailer to significantly invest in indoor vertical farming. Vertical farmers say their method brings higher yields while using less water and land. https://t.co/cTfPtuQEUV 

Chris writes:

This is just my own curiosity. This is not for diagnostic purposes, or representative of any trend.

Is it possible to have COVID and not test positive on serial at-home rapid antigen tests?

As of yet, I have never tested positive for COVID. And I find that extremely unlikely. At the risk of moral opprobrium, I’ve been going out plenty. New Year’s, long weekends, birthdays…buck wild. I’m a 38-year-old vaccinated male with no pre-existing conditions who lives alone and works remotely. (And skipped Christmas with my elderly family.)

But I know I have been exposed to Omicron…and Delta…but really Omicron is the relevant one here. I’m in Chicago, and we were right behind New York in terms of the wave. Literally all of my friends have had Omicron. Literally. I can name 50 people off the top of my head—and one of them I was with in a broom closet the day before he tested positive.

And yet no positive test for me. However, the week leading up to Christmas, I had some vague illness that sure matched the description of Omicron in young…ish…vaccinated individuals. PCR tests were extremely difficult to come by (see tangential link below), so I had to resort to 3 rapid tests. I had symptom onset on Sunday evening, and swabbed on Monday, Wednesday, and Friday. And no positive result.

Is it possible to have mildly symptomatic COVID, but not test positive on these tests? I’ve just not really heard of that happening…and unfortunately, I couldn’t get a PCR as a control.

(Tangential link: I considered going to one of the many, awful, scammy-looking test sites that have popped up. I am glad I didn’t waste my time. https://blockclubchicago.org/2022/01/26/ohare-clinical-lab-another-chicago-based-covid-testing-company-which-got-186-million-from-the-feds-is-under-investigation-as-complaints-pile-up/ )

Anthony writes:

‘A Menace to Public Health’: Doctors Demand Spotify Puts an End to Covid Lies on ‘Joe Rogan Experience’

I hope that you remove your Podcasts from Spotify if they don’t act ro stop misinformation.

# # #

Susan writes:

Hello Twivvers,

I’m in Minnesota so I have you all beat in terms of cold weather! I have been listening to your podcast for the past year and appreciate all your work to help educate the public on these issues. I advise employers on covid-related workplace policies and vaccine mandates, so I have tried to dig into the science in order to provide informed advice. Not only is your podcast a fantastic resource but it has helped guide me in terms of who to listen to (AND NOT) on science/med-Twitter. One expert I follow, aside from all of you, is Professor Akiko Iwasaki who has been working on mucosal vaccines. I’m hoping you will cover her new study on intranasal spike vaccine booster even though it is a preprint. 🙂 I would like to understand it better and hear your opinions on the promise of this type of vaccine, which would seem to be a “game changer” (agree this is an overused phrase but it might apply here).


While I have your attention, there is also one question that I can’t seem to get my head around. That is, how to square the notion that if we vaccinate enough people, the virus will eventually not have anywhere to go and die out, with the notion that more vaccination puts a selection pressure on the virus causing it to evade immunity.  This is a line from Apoorva Mandavilli’s article today in the NYT:

“As more and more of the world is vaccinated, evolution will favor forms of the coronavirus that can sidestep antibodies and other immune defenses.”

I would love to understand this better and as well as hear how to stop this from happening.

Thank you very much for all you do.



Minneapolis MN 

Patrick writes:

Dear TWiV,

Greetings from Arlington, MA.

I don’t understand how there is so little discussion of the relevance of the length of incubation periods to the effectiveness of vaccines.

Months after getting any vaccine, the antibodies active in the blood are largely irrelevant because of how much they have reduced. It’s the more rapid activation of the adaptive immune system from prior immune memory that fights off the disease, but that takes roughly 5 days on average to ramp up into full gear.

The really great vaccines — like Smallpox, MMR, and polio — are against viruses with relatively long incubation periods (Smallpox 12, Measles 11, Mumps 16, Rubella 14, Polio 7). The immune memory from the vaccine always wins in those scenarios, even with the inherent variability.

But with COVID having only an incubation median period of 5 days (and possibly 4 for Omicron), and infectivity even before symptom onset, the immune memory will often lose the race and leave us with infectious and diseased individuals, though protected in time to usually avoid hospitalization and death.

Do you see any flaw in that logic?

Thank you for all your good work.


Jay writes:

Since you got a kick out of furniture restorations I thought you might like this channel of art restorations: https://youtu.be/5G1C3aBY62E 

Cheers, Jay (Melbourne, Australia)