system
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human
Can a person with the flu vaccine still spread the flu?

I was just wondering if you are vaccinated and you are exposed to one of the strains of virus the vaccine covers, and your body fights it off, is it possible in the period of time that your body is fighting it off for you to spread the virus to others? 

So I guess I’m wondering at what point you become contagious? 

i know viruses hijack your cells and eventually lyse your cells once they have used it’s machinery to replicate, is it at this point at which you become contagious? Once the viruses reach a certain “dosage” from replication within your body?
gpt
The flu is spread airborne by being in the bodily fluids you expel eg. suspended in your sneeze-water. The entire time you have the virus there is SOME in your bodily fluids, but what makes it contagious is your body facilitating spreading that fluid (there is also a threshold point of viral load in fluid, where there is enough virus in that fluid for it to be an effective contagion in a new body, but that is a hard thing to pin point down and depends on a lot of factors in the environment and the new body it enters).

The vaccine does not make your body block the virus at the door, it just keeps it in an alert state so that its really quick to fight the virus off. What this means *ideally* is that its so quick you fight it off without really reaching that state of spreading viral fluid around. What it more likely means is you fight it off fairly quickly, and so the time the virus is transmittable from you is significantly diminished (ie you are briefly contagious, which significantly *reduces* you spreading it).