Matt writes:

Good morning,

I sure enjoy your fascinating Immune podcasts!

I have not heard of any mucosal delivery vaccine candidates for COVID-19.   Since this virus does so much of its damage to the lungs, I was wondering if such a route might be helpful, such as intranasally.  The attached article seems to be a nice summary of the state of mucosal delivery vaccine science.

What are your thoughts?

Thanks again,


Robin writes:

I sent my first email question, included below, to TWIV but then I found and listened to your Immune podcast, Covid -19 part 3.  You mentioned that many people DO NOT seroconvert meaning I think that their body does not recognize the covid virus as a threat and therefore does not take the steps to fight it.  This was one of the questions I had but then I want to know if you think such non-seroconverters will continue to carry this virus, silently, their entire rest of life.  Are there other infectious viruses that some folks carry silently?  It seems that the more we find out the more questions arise.


San Pablo

Physical science teacher with a life science education and just enough knowledge about the subject of microbiology to possibly be dangerous.Emoji

David writes:

Hi Immune hosts,

I have been listening for the last 10-15 episodes which I started a year ago or so,  to learn some immunology since my field of cancer biomarkers has made a sharp turn in that direction.  However, now, with COVID 19, I am reading and learning some virology (my last formal class in virology was in med school over 30 years ago).  I now run an anatomic pathology lab, and I am boarded in anatomic pathology, but not in clinical pathology where they study and perform serologic testing.  Since I use a lot of antibodies in my tissue biomarker work, and know how challenging it can be to get specific antibodies, I am not too surprised at the lack of respect we are seeing for serologic testing for spike protein or other viral proteins.  I am more surprised about all the concern that the antibodies may not have neutralizing activity.  I understand the cultured cell tests for neutralizing activity.  But if most of the antibodies generated by infection did not have neutralizing activity, with over 1.5 million cases in the US, wouldn’t we see hundreds of cases where health care workers got re-infected and became symptomatic?  I have not see even a single case report of recurrence that is both sufficiently spaced (say, test positive after >30 days, with negative tests in between) and symptomatic (say, requiring hospitalization).  Are these cases out there and not reported?  Or if not, isn’t this pretty compelling evidence that the vast majority of infected individuals making neutralizing antibody (which could be detected by serology)?

Thanks for considering this question.




David L. Rimm M.D.-Ph.D.

Professor of Pathology and Medicine (Oncology)

Director of Translational Pathology

Director, Yale Pathology Tissue Services

Dept of Pathology

Yale University School of Medicine

Mei Yi writes:


I am a Bi 115 (Virology) student from Caltech. In Immune 29: Immunology of COVID-19, you guys mentioned that IL-6, IL-1, and IL-8/TNF were upregulated in patients with COVID-19. I was wondering if these proteins are specific to the response of COVID-19 or that it’s just part of a general inflammatory response. Is there a protein or group of proteins that are specific to COVID-19 and would help us identify that an inflammation is caused by SARS-CoV-2?

Thank You,

Mei Yi

Sarah writes:

My name is Sarah Hasan, a medicine resident training in an NYC hospital. We have been at the forefront of the COVID epidemic, it’s been surreal but thankfully at this time we are trying to get back to normal, but who knows how long that will last. I have really appreciated listening to microbe tv, I have definitely learned a lot from you all! 

I have been curious about how SARS-COV-2 is able to do asymptomatic shedding. How is the virus able to replicate easily while the host does not have symptoms? Correct me if I am wrong, but I assume that symptoms only occur once the immune system is alerted, so going with that reasoning, I am assuming the host is able to basically replicate with an invisibility cloak for many days. Do you have any insight into this? I know that other viruses like the flu and herpes do have abilities to hide from the immune system so wondering whether you could also extrapolate from other examples? I would really appreciate some answers to this as I have been looking all over the internet and could not find anything. 



Sophia writes:

Hello beautiful Immune team

hope you are all well. I saw this in the news:

not sure if the above is worth talking about but my question is: if we are concerned about vaccine enhancement with this virus is the above study a good idea? or is vaccine enhancement dealing with another arm of the immune response?  any ideas? maybe a naive question? 

all the best from Greece

9 degrees C, windy and rainy, great quarantine weather!

following to my previous email here is another study that does shed light and does explain the death rates in different countries through the BCG lens:

in essence, countries with robust BCG vaccination programs  since 1922 seem to have protected their elderly population somehow (does it still work? well, it looks like….) through this vaccine. If this is the case I have hopes for Africa.

ps great immune episode last time. greetings!


Sophia writes:

Ηι again

you don’t do picks of the week any more but when you go back to doing them here is a nice story/colouring book on immune defences on viruses:

(although I am not sure what the cytotoxic gun is about). For a more intellectual and complete version I recommend twiv597. An outstanding and most enlightening episode!

all the best!