I'm so happy a study like this has finally been completed. It echos what many have been saying for years, that vaccines are just not needed yearly. Immune systems aren't forgetful and don't need yearly reminders. It would be wonderful if they continued this study to see how much longer the vaccine lasts. @Suki - about your Hubble, from your description he sounds like a non-responder, which would mean that he will never acquire adequate levels of antibodies against CDV. If that was the case, it won't matter how many vaccines you give; he will never be protected. A weak responder would eventually develop an adequate response after more vaccines. Have you ever ran a titer soon after vaccination (2-4 weeks after) to see how he is responding? Jackie [Posted in FML 7505]