You are doing more harm than you know.

Seriously. Watch this for 10m and you will be enlightened.


Start at 1h34m 50s
AND at the cutaway,
skip to 1h43m 39s (MAREK's DISEASE - leaky vaccine used...)

SUMMARY: An expert, Andrew Read, from ASU uses Marek's Disease in chickens to explain why a vaccine which does NOT stop replication or transmission will alter the environment encouraging changes which make the virus more lethal.

The fact that the third gen vaccine is holding at the moment "is why your chicken nuggets are cheap".

Basically, the virus went from being mildly lethal in the 70's to unvaxxed chickens all died REALLY quickly because the virus learned to thrive in the environment of vaccinated chickens.