Azim writes:

Thank you again for the work you are doing. Your knowledge exchange efforts are unparalleled and certainly a bright spot in this situation we find ourselves in. As we see COVID activity increase in Canada, I can only appreciate the work you are doing in helping us out around the world.

I had a question about COVID vaccines and was wondering if anyone on your teams would have an answer? Considering the target for an effective vaccine was 50% and we are assuming from press releases that two dose mRNA vaccines will be 95% effective, do we have any data available on how effective a single dose vaccine would be? Assuming it’s greater than 50% and with consideration of production capacity delays, would it be better to immunize double the number of people with half the dose initially? And by ‘better’ I would mean decreased transmission rates and decreased morbidity/mortality/disease severity.

I’d also be interested in knowing whether previous infection with SARS-CoV-2 changes the immunity associated with a single (or two) dose vaccine series. Hopefully when the studies are released they include this information.

We would need background information to be able to model each scenario out and determine the optimal strategy. Hopefully Dr. Griffin or someone from your team can help enlighten us.

Finally, if your team has any information on seroprevalence it would be very helpful to know. We’re assuming 10 infections for every case, meaning the US is quickly approaching 50% of people being infected at some point. Certainly a significant number in and of itself, though the nature of spread is non-random.  

Thanks again. There appears to be a light at the end of the tunnel and I look forward to listening in on Sunday afternoons to learn more about all of those other viruses you normally discuss.



Azim Kasmani, MD
Resident Physician, Public Health and Preventive Medicine
Queen’s University

Mark writes:

Vincent and Crew,

After listening for several years, I finally got around to donating to via

The best part that you should definitely be hyping more: on the donation receipt is the autograph of the fabulous Dr. Daniel Griffin – that alone may have been worth the donation!

Keep on keeping on, as my mother always says.



KC writes:

Hi from Winnipeg,

Thanks for all the time and work you put into this amazing podcast. I always look forward to new episodes. You all deserve your own daily tv show on a big tv network.

I have a question for Daniel Griffin regarding N95 masks. If you are only issued one N95 mask per 12 hour shift what’s the best way to prevent contamination when you need to remove it for eating and drinking? It’s scary to see so many fellow healthcare workers contracting Covid despite their best efforts at wearing appropriate PPE. Any information would be greatly appreciated. 

Keep up the great work 🙂


Irina writes:

This Irina Yakutenko, science journalist from Berlin. I have just listened to the TWiV episode about minks and I want to make some brief remarks. First, there are mink farms in the US and there already have been a couple of outbreaks there. For example in Utah ( ). However as we all read a lot of news about culling minks in Denmark or in the Netherlands and Spain, I never saw any news about culling minks the US. And one can assume that there are strong economical reasons for that. As far as I know, one of the biggest purchaser of fur is China ( Although the Chinese themselves produce a lot of fur, they also buy a lot of American and European fur. And because mink farming in China is rather safe in the context of the virus spreading, unfortunately one can await new outbreaks on American farms. And as you have said in the episode, these farms are the perfect reservoir for cultivating new versions of the virus.

Best regards,


Jim writes:

Hello TWiV folks.  I have not missed an episode since I started back in March (April?) with number 598.  I don’t follow everything, but I think I have a much better feeling for the issues surrounding SARS CoV-2 than I would have without.  I also like it when you talk about other viruses, e.g. the ones discussed in zebrafish on today’s podcast.  

The discussion by Vincent and Rich about science, politics and morality (ethics is maybe a better word) was insightful and necessary.  

I want to say a bit about risk taking in today’s world.  I am totally on board with masks, physical distance and low density meetings.  These help me stay safe, but more important is that I am doing my thing to protect the community.  Still I will take certain risks that others may choose not to take.  For example I have met with a friend for lunch; we sit outside at opposite ends of a relatively long table.  These are risks that we have each agreed to take for ourselves—the behavior has no (or almost no) effect on others.  A somewhat more risky behavior involves tutoring a high school student in math.  We tried to do this on line, but it really didn’t work.  So we meet once a week in a large room, wear good masks, and mostly keep some distance.  I am willing to balance the risk of infection against leaving this student without the help needed to learn at this time.  I certainly would not meet like this for less important reasons.

The gist of what I am saying is that we each individually have to balance the risks against the need to live our lives.  Risks should be individual and not communicated to others who are not also agreeing.  My motto here is to be prudent but not obsessive.

Keep the show going.  You communicate well even to this 79 year old mere mathematician.



Ryan writes:

There is a story out there that an Anti-Vax Bishop is scaring people away from the possible COVID-19 Vaccine by using the religion scare to not get vaccinated, Yes its the fetal cells conspiracy in vaccines.

Citing ethical concerns about the use of fetal cells in vaccine development, Bishop Joseph Brennan of the Diocese of Fresno is urging Catholics not to “jump on the COVID-19 vaccine bandwagon.”

In a video shared by the diocese this week, Brennan said that some of the researchers racing to produce a coronavirus vaccine have made use of cells derived from an aborted fetus, and perhaps other “morally objectionable” materials.

“I try to maintain a joyful spirit, so I don’t like to rain on anyone’s parade,” Brennan said. “But I’m going to rain on a parade today: the vaccine parade.”

In his message, Brennan said the use of fetal cells at any stage of a vaccine’s development means Catholics cannot avail themselves of its scientific results.

“I won’t be able to take a vaccine, brothers and sisters, and I encourage you not to, if it was developed with material from stem cells that were derived from a baby that was aborted, or material that was cast off from artificial insemination of a human embryo,” he said. “That’s morally unacceptable for us.”

Vr: excuse me oh holy one, the mRNA vaccines are not made in any cells. Go back to school. Likely talking about MRC-5 cells, made in 1966 from the lung cells of an aborted fetus. Will have to check what cells other vaccines are made in. Point is, don’t trash all of them if you don’t know how they are made.

Jacob writes:

Hello Twivers,

It is a sunny day in Boise, Idaho.  Temperature is about 72 degrees F.  Sorry I do not know the Celsius temperature and am too lazy to calculate it.  Thank you for bringing the Great Barrington Declaration to my attention.  I found it to be a very interesting read.  As you pointed out there are no virologists among the signatories.  The other two groups of professionals noticeably absent are medical historians and psychologists.  A careful examination of the historical records shows that pandemics create fear and at times panic.  Now you may tell me that we do not have a complete historical record of all the pandemics that have occured over the past 3000 years.  Fair enough!  So I suggest that you look around.  I see lots of fear around me.  This should not be a surprise.  Fear of the unknown terrifies most people.  Fearful people tend to not  go out and make merry.  Nor do they tend to spend money.  The economy is sinking because of fear.  This is not a brilliant thesis.  It is common sense.  Or to be more precise, the amount of sense that God gave a mule!!  If you require evidence, compare the economic recovery of San Francisco and Philadelphia after the 1918 pandemic.  Or pick up any book on hazard communication.  Rule one is tell the truth!  Rule number two is do not forget rule number one.

The Barrington declaration reminds me of a similar manifesto signed by Max Planck and many of the most brilliant scientists in Germany just after the beginning of the First World War.  It was in support of Kaiser Billys war.  It did not take long for these gentlemen to realize signing this document was a bone-headed idea.  Einstein did not sign this document.  Obviously he showed great wisdom.  It just goes to show that just because you have a lot of letters behind your name does not mean you are not a dunderhead!

I was going to end this letter here, but I just finished listening to 673 and was a little riled up by the letter written by Megan. 

[Megan is Montana physician dealing with misinformed mayor and coroner ]

 Here is my two cents.  Do not back down!  Stand your ground.  Do not show fear.  This is what they want and you should not give it to them.  This virus is highly infectious.  Remember the paper written by Mark Lipstitch back in January.  80% of the entire world within 18 months was the prediction.  Looks like he will be hailed as a genius for this prediction.  Soon the virus will touch everyone.  What will happen to the deniers when they start getting sick?  Hmm Interesting question.  What does the historical record tell us?  Fear!!   followed by anger is my guess.  My opinion is there is no way to stop it.  The human race is taking a bath in humility.  Mother nature has her big old scrub brush out.  Don’t forget behind the ears.

Just to show you that all the dunderheads do not live in Montana I have included this link below from NPR.

I will end with one of my favorite sayings from the Borg.  Resistance is futile!

Sorry I just had to say it.


Arjan writes:

Dear team TWiV,

First of all, may thanks for the high quality science communication you all do. You make such a wealth of scientific information accessible to the public.

In TWiV676, you discussed a paper blaming Neanderthal genes for causing severe forms of COVID-19. What’s puzzling to me is the fact that the Neanderthal haplotype is also present in the Indian subcontinent and Indonesia, parts of the world never inhabited by Neanderthals. And not only that, but there, that haplotype is fourfold more frequent than in Europe, which is known to have been inhabited by Neanderthals. As a theoretical physicist, I’m no expert in hominid migration, and I assume neither are you, but I don’t know of any later human migrations that might explain these findings. And that, to my mind, invalidates the blame laid on the Neanderthals (if you ever could do that, of course).

And since antibody-enhanced disease also got a mention in episode 676, I’ve been wondering how that would be possible if there only is one strain as is the case with SARS-CoV-2. Wouldn’t AED already show somewhere in the first infection when antibodies arrive at the scene? And if it were possible to have AED with a single strain, wouldn’t that be a concern for any viral disease?

Keep up the good work!



Burkhard writes:

Hi Twiv-Team,

Listening to my riding-in-the-rain-to-work-podcast, I was wondering if this might be interesting in the context of the email from Michael Essex in twiv 676. Thank you so much for your awesome podcast!

Burkhard (urologist in berlin, germany)

Matthew writes:

Dear Vincent and team

My wife and I are big fans of your show and the various panel members. Thank you for your expertise and humour (we spell it with a “u” here).

We would be interested to hear your panel’s views on what is going on in South Africa with SARS COV-2. South Africa first peaked in July 2020 with about 14 000 reported cases a day (population of around 60 million). We are now on a very low level lockdown (what they call “level 1”) of a five level lockdown structure (five being everyone stay at home, don’t buy alcohol, don’t go out at all etc, level one being everyone carry on as normal, but wear a mask, wash your hands and practice physical distancing of six feet and avoid large gatherings, particularly indoor ones).

At least two recent studies (an example is cited below) seem to suggest that in urban areas (such as Cape Town and other cities), up to 46% of randomly sampled members of the public have had exposure to the SARS CoV-2 virus, which causes Covid-19, suggesting that far more people have been infected without even knowing it. Many epidemiologists in South Africa are now saying that these studies show that the infection level in South |Africa is actually really high, but  many people are completely asymptomatic. Our numbers have been relatively stable for the past several weeks (between 1000 and 2000 new daily cases and daily deaths usually well below 100). Many people in South Africa are concerned about a “second wave” such as the ones European countries are experiencing, and fearing another harder lockdown in South Africa, and the economic devastation that would wreak (over 2 million people have lost their employment since March 2020 in South Africa as a result of the lockdown, and our economy is in terrible shape, at least partly because of the lockdown measures).

Does your team have any insights about the apparently high level of infection in South Africa, compared with a relatively low level of symptomatic patients? Is this a worldwide phenomenon? I have also read some experts who contend that the BCG vaccine that is given for tuberculosis in South Africa (a vaccine at birth is mandatory) may have some impact on the human immune response to SARS Cov-2. Any insights you may have into the South African situation would be consumed with interest.

Thank you for the opportunity to ask this. Don’t stop what you and your team are doing, please!

Regards from sunny and warm Johannesburg South Africa (25 C going up to 30 C today), 30 October 2020


Jay writes:

Hello everybody,  I’m having a hard time understanding the term viral equilibrium.  In my efforts to understand, I keep coming across that it has something to do with the virus in an individual patient.  I’m looking to find out what happens when a virus goes throughout a population uninterrupted or if successful vaccination is not achieved. Now with coronaviruses it seems that reinfection is possible. So in that case it seems herd immunity may not be possible. What are we left with? If a virus is left to go throughout a population long enough would it ever reach a point where it can no longer create disease? And if so would it establish a symbiotic relationship with the host? Would that be considered equilibrium? I wonder if these viruses were once dangerous to bats? I have no accredited scientific background, just curiosity and my garage lol. 

Speaking of curiosity, how about some science fiction thoughts. Could this ever be possible? Let’s say we take the measles virus, strip it of its bad parts, bolt on the antigens of the virus in question. Allow it to replicate and keep its transmission.  We could call it a contagious vaccine.  If this were actually possible do you think it would catch up and even out pace the pandemic? logistically we could let nature do the work for us. Listening to you guys talk about the polio vaccine giving other people polio triggered this thought in my head. Anyways I love the show and I’ve been listening from episode 596 til now with earlier episodes in between the new ones. Keep it up and I look forward to each show!!!!!  



Agda writes:

Agda writes:

Hi Vincent,

since you guys discussed synthesizing RNA in vaccine development, I thought this might be interesting:

Also I’d like to suggest Larry Moran’s very insightful science blog as a pick of the week, he’s been doing it since 2006 and I really appreciate having access to science blogging in addition to science twitter, as you guys might also appreciate since you champion longer science communication formats!

All the best from Berlin,