Vaccinating Adult Chickens with Mereks??

[nic_xxa]

Hi, recently one of my 2 year old hens passed away after a necropsy and testing another hen. Both tests show that have/had mereks disease. I know most people typically vaccinate chicks as soon as possible, unfortunately in this case I do not believe they were vaccinated.
I’ve seen a lot of back and forth discussions on whether vaccinating adult birds is necessary. I have around 15 birds which I’m assuming they all have contracted the virus.
For starters I’m not sure if all of them have been vaccinated or not so if I decide to vaccinate them will double vaccinating them be an issue?
So is vaccinating them necessary to help them live long healthy lives? Will it contribute anything since I’ve seen debate that once they’re older it does virtually nothing but some people say it does.
So for those with mereks positive flocks or anyone knowledgeable please help and share some insight.

 

[Eggcessive]

The vaccine would only help if they were never exposed to Mareks. It is best to vaccinate day old chicks at the hatchery, and keep them free of any exposure for at least 2 weeks. The vaccine can be repeated once or twice for hopefully better resistance, according to some literature I have seen.