For anyone who absolutly does not want to vaccinate, one of the worlds formost experts on the sebright wrote a good book on the birds, He said sebrights are extreamly suseptible to mereks disease, , he ran one white turkey with all of his new chickes the turkey shedds a mlder form of the virus that innoculates the chickes from a later more severe form.
I just vaccinate , I never want to witness what I did several years ago, I had never felt so helpless and sad. I get both mereks and newcastles vaccine, I vaccinate after they are dry and standing for mereks, about 2 weeks later I give the newcastles in an eyedropper. you can do them both at once like hatcheries do, follow directions as prescribed, you can put it in vaccine form or add it to water. I use eyedropper cause I feel Its just safe.