Thread by @MonicaGandhi9

Why so excited about IgA? Wanted to explain immunoglobulins (antibodies) a bit to explain why the real-world data is showing us that the #covid19 vaccines block transmission. There are 5 different types of immunoglobulins in human body: IgA, IgM, IgG, IgD, IgE. You hear a lot

about "antibodies" and neutralizing antibodies after #covid19 infection & #covid19 vax, which refers to IgG immunoglobulins. But function of IgA antibodies is to protect us at the surfaces that face the world, the "mucosa": nose, mouth, gut, genitals, etc
nature.com/articles/nm1213

Obviously, 1st line of defense against respiratory pathogen like SARS-CoV-2 is where you encounter it (nose/mouth) so IgA responses there after vaccination would help you fight the virus the minute you are exposed and, importantly, limit viral replication so you can't pass it on

In movies (like Contagion where actors had vaccine administered intranasally) and also with #covid19, there is interest in nasal vaccine. But we knew from other systemic (given by shot) vaccines that IgA (line of defense in nose/mouth) is generated
cvi.asm.org/content/23/6/4…

And now we have at least 3 papers (tell me if there are more!) showing us that IgA antibodies are induced by #covid19 vaccines: The first actually shows us that vaccines induce IgG antibodies that happily get into saliva to protect you there & IgA in most:
biorxiv.org/content/10.110…

Tweeted 2nd paper last night but mRNA vaccines in pregnant and lactating women induced IgA (which is secreted in breastmilk by the way) and IgG. And then you know my favorite paper on this is where authors literally biopsied lymph nodes after vaccination
medrxiv.org/content/10.110…

and saw germinal centers forming memory B cells to vaccine which has implications for long-term immunity to #covid19 (reviewed here more) threadreaderapp.com/thread/1370413…), but this paper also showed us that IgA produced at high levels after vaccination!
researchsquare.com/article/rs-310…

So no WONDER we are getting us all this accumulating data that the #covid19 vaccines reduce transmission with mucosal immunity being induced. Protects us the vaccinated from viral entry and protects others from us transmitting since viral replication inhibited at mucosal surface.

So, if you have a "positive PCR" after vaccination, would be important to know viral load in that swab (which you can quantify by knowing how many cycles the PCR machine has to go through to amplify that virus, CT threshold) to know if you could pass it on
medrxiv.org/content/10.110…

Above paper & below would argue it will be hard for you to pass it on if you get exposed to #covid after vax with that effective mucosal immunity. So if you're not really re-infected & not infectious, isn't it like proverbial tree in forest falling
medrxiv.org/content/10.110…

with no one around? Can it be heard? Mass asymptomatic testing after vaccination will not be indicated in my opinion. If symptomatic, test and even sequence thereafter if positive. And do know that vaccine failures will happen but will be RARE
verywellhealth.com/second-cases-o…

TESTING AFTER VAX: Before anyone tells you there is a breakthrough infection, ask 1) was the person asymptomatic?; 2) what is CT value of the PCR test if PCR? If symptomatic & infectious by CT value, call it breakthrough; if not, immaterial (& why mass testing after vax problem)

Sorry, wanted to explain this more clearly. Looks like breakthrough after vaccine of getting COVID is very rare. If you don't have symptoms and you can't spread it, that is not a breakthrough but likely you being exposed and fighting it right away at the nose level

So, if you look at info in thread above, you can see that viral loads in your nose can be very low after you get tested after vaccine. Is that "infection" or is that you fighting the virus you were exposed to & stopping it in its tracks? And if you can't spread it & you don't

have symptoms, what is the point of testing and calling that a "breakthrough infection" (like perhaps that Israel case B.1.351 after vax -did the person have symptoms? What was the viral load in the nose & could they pass it on?). So, in my opinion, breakthroughs (true) =

1) person with symptoms + 2) person having a viral load high enough to spread (which can be told by looking at a certain value in your PCR test if they tell you or doing a rapid antigen). We will be calling a lot of specious breakthroughs if mass asymptomatic screening after vax

In my mind, this is a KEY point and why companies, counties, schools, etc. should reconsider this strategy of mass asymptomatic screening after vax. Asymptomatic person who can't spread it is not in any way a threat but will be called a breakthrough on the vaccine & upset people

1 more point: the virus starts to replicate in your nose and you block it off by your immunity if you are vaccinated (that is why I discussed IgA). But a PCR test can pick that up and say you are "positive" when you really were doing exactly what you were supposed to do: kill it