Carson writes:

Hi TWiVers and Daniel,

I’m sending this to both emails because I’m not sure who could better answer these questions.

1) I know research shows that long-term vaccine side effects generally start within two months of vaccination. Personally, I’m very comfortable with the safety of the COVID vaccines and am thankful to be fully vaccinated with Moderna. However, I wonder if the argument could be made that something like cancer wouldn’t be seen for years. 

I know that in general, carcinogenicity can be difficult to determine, especially for things that everyone is exposed to. I don’t think that anything points to the COVID vaccines being carcinogenic, but how would we be sure? Is it enough if they’re not carcinogenic in vitro or in mouse models? 

It just seems like anything greater than a year or so out would be really difficult to link back to the vaccine in the first place, even if it did cause it. Again, I’m confident in the safety of these vaccines, but these questions still nag at me.

2) With regard to the clotting disorder that’s possibly linked to the AstraZeneca vaccine – just for clarity, when you say that the rate of this is no higher than in the general population, do you mean that you’d expect the same number of cases of that specific clotting disorder in the same time period from non-vaccinees? 

Also, if it were not related to the AstraZeneca vaccine, wouldn’t we be picking up the same thing with the other COVID vaccines? 

Given that it seems to predominantly impact women between 20-50, I’m interested in how many of the patients are on hormonal birth control. I myself am 25 and take combination birth control pills, which I know can increase the risk of blood clots – though I don’t know if they would be the same type of clot. I don’t want people to be afraid of vaccines or birth control as both are live-saving, but I’m curious nonetheless.

Thank you for all you do,


Carson writes:

Hi TWiVers,

I’m currently listening to TWiV 740 where you mentioned trying to make one episode a week about non-COVID topics. I’m excited! I only found TWiV during this pandemic, but I’m a research assistant in an infectious disease/immunology lab, and I’m starting a microbiology PhD program at UAB in the fall. Hoping to focus on virology or viral immunology 🙂 

There are a few topics I’d love to hear y’all discuss.

1) I’ve seen a lot of buzz around this HIV vaccine – is it warranted? I feel like I often read about “scientific breakthroughs” only to never actually hear about them again because they didn’t live up to the hype.

2) I would love to hear more in-depth discussions on Ebola & the current outbreak. I still need to go back and listen to your episodes from the 2014 epidemic, but I want to keep up with the current research as well. I was admittedly disappointed when you started discussing it the other day (731) but shortly moved on to COVID. 

Of course, I’m excited to hear anything you discuss, but I’m particularly interested in those two topics! I also loved the recent episode (725) on flaviviruses – dengue is probably my favorite virus.

Thank you for all you do to communicate science,


Abby writes:

Apologies if this has already been shared!

FDA Grants EUA to COVID-19 Screening Device for Asymptomatic People

SOURCE: Medscape

PUB DATE: March 22, 2021

Abby, MSIS
Social Work Office of Research and Public Service (SWORPS)
Software Development and Systems Engineering Unit

Abby writes:

Dear 💛VDRKB💛,

Got dose one o’ the Pfizer yesterday, or as I’ve been saying, “D1P.”

Huge space in Nashville’s “Music City Center.” Garage parking—free, when exiting with your vax card. Clear signage, staffed at every turn: FEMA, Homeland Security, EMT, FD, PD, HD. You name it, they were there. 

They’re prepared for lines as long as the Appalachian Trail with floor markings and even chairs as you near the end, but we whizzed right through. We were in and out within an hour. Scheduling our first dose was simple and the appointed time was a forgiving, one-hour block. No appointment needed when we return for D2P, we just show up any time between 8-4 pm, any day within the range. The site is reporting ~2,000 shots administered per day. 

It was a sparkling example of efficiency and competence. 

And of course, I wore my TWIV shirt…

<Vax – Dose1 Pfizer – Metro Nashville.jpg>

Regina writes:

Hello TWiV people, 

I have a very important question. What the hell is a person-day? Is this the immunology version of a lightyear? 

Backstory: My boyfriend and I were finally able to get our first dose of the vaccine and now he is asking “So when are we protected”. Of course my answer was “two weeks after the second dose” because I am all about those expert recommendations. But, because we are both stubborn humans who love to be correct and cannot wait to go to a gym, he started sending me papers, such as “Early rate reductions of SARS-CoV-2 infection and COVID-19 in BNT162b2 vaccine recipients” I read the paper and come to the same conclusion as before (I didn’t become a hermit for a whole year to mess up now over a couple of weeks). BUT, I came across the idea of a person-day and my brain cannot compute. I then tried to find a prospective study looking at the efficacy after a single dose and found this paper, “Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers — Eight U.S. Locations, December 2020–March 202” in the MMWR. And again with the person-day thing. I study plant immune responses and we don’t have plant-days, leaf-days, nothing like that. So please help me understand what is happening here. 

A baffled, partially vaccinated nerd from 80 Fahrenheit 10000% pollen Birmingham Alabama, 


PS I am sure I could google this, but where is the fun in that when the TWiV team could potentially answer my question instead?

Steve writes:

Hi Vincent and fellow TWiVsters.

I would imagine that the singing enthusiasts in the team must be familiar with the highly imaginative productions of ‘Randy Rainbow’, but I don’t recall them being mentioned. There are so many brilliant ones to choose among, but I thought that Vincent, in particular, would love this one: 

It would make a good alternative title music for the show while the pandemic continues. It’s a shame YouTube’s algorithms didn’t alert me to ‘RR’‎ sooner, but there are many works of sheer genius to dip into in the repertoire he has been able to produce in his own home during the ‘lockdown’.

A great listener’s pick: I think.

Many thanks for all your good work. I’m afraid that I can’t retain very much of the information, but it is very enjoyable listening for its own sake. 🙂

Best wishes,


In Luton, England: where it is looking nicely Spring-like, with the plum/blackthorn blossom out and the sun shining.