For those who are choosing to raise chickens organically for their own purposes, and not for market, take into consideration all that is needed for sale. Your chickens should be fed an organic diet, and allowed to free range.
It is entirely up to the owner whether or not they feel their chickens should be vaccinated or should receive medicine when sick. A free range chicken on a healthy diet is unlikely to get sick. The best organic chicken is ultimately a happy chicken. Keep your flock healthy and happy by allowing them daily access to a pasture, as well as giving them attention.
Many do not realize that chickens are very social creature and enjoy the human interaction, especially once they become comfortable with that human. Be sure to take all safety measures before allowing your flock to free range to protect against unwanted predators, although allowed to free range the flock should still be monitored.
Additionally, be sure your flock has a coop or house to retire too, or flee to if they feel threatened. And last but not least, always make sure your flock has access to water, and be sure to supply fresh and clean water daily as many contaminants and bacteria build up in water left unattended.