Both inactivated and modified live vaccines based on whole Chlamydia organism are available as part of multivalent vaccine preparations. Vaccines are effective in protecting against disease but not against infection [Wills et al, 1987]. No reliable data are available to compare efficacy of inactivated versus modified live vaccines.
Vaccination should be considered for cats at risk of exposure to infection, particularly in multicat environments, and if there has been a previous history of Chl infection.
Vaccination of kittens generally begins at 8-10 weeks of age with a second injection 3-4 weeks later. Limited information is available about the duration of immunity. There is some evidence that previously infected cats can become vulnerable to re-infection after a year or more. Annual boosters are recommended for cats that are at continued risk of exposure to infection.