I just bought two chicks. They are being kept from my hens(7 and 5 years old). The chicks look healthy and came from a farm store with good biosecurity (disinfectant brooder between batches, remove sick hens, don't except returns). However, they have not been vaccinated and my adult hens have always been isolated with no cases of disease. Should I vaccinate both the adults and chicks? Is biosecurity and isolation is enough?