Ok, here we go again. Vaccines, are they preventive care or a false security. Are they contagious to other birds?
I have always understood that once a bird is injected with a live virus, that they will pass along this "shedding" if you will, to the next unvaccinated bird, chickadee or crow.
Now I am not saying this IS what happens, yet could it. I recently gave information to a fellow BYC member that was attacked by other BYC members and this has brought me to the next paper I am going to write.
So far here are the basics that I've compiled, I know I can be wrong, but realizing this makes me human and uneducated. If so, I will apologize.
Here is a site where it mentions what I'm saying!


(And I quote)
Marek's disease
It has been demonstrated that the vaccine only prevents the appearance of Marek's disease tumors and paralysis. It does not prevent the birds from becoming infected with and shedding the Marek's virus.
Fowl Pox

Do not vaccinate unless you have a problem on your farm or in your area. The virus is spread from bird to bird through the bites of blood-sucking insects (such as mosquitos) or through wounds and scratches by the birds when fighting. If there is a heavy mosquito infestation in an area, small flock owners may consider vaccinating with fowl pox vaccine.
State approval is required prior to vaccination. Do not vaccinate unless you have a problem on your farm or in your area.​
That is because it spreads from bird to bird, dust, feed bags and clothing.

However, in the following days, vaccinated birds will horizontally shed the vaccine to pen mates. The horizontal transmission will be variable and there will be additional changes in the maternal antibody levels, further complicating the flock's reaction. The same principals apply to spray vaccination

Please feel free to write and share information, pages or questions!
Thank you!