Here is a link to a US group that is studying duration of immunity for rabies vaccinations using challenge studies:
Duration of Immunity Study for Rabies Vaccine - Rabies Challenge Fund
From their February 21, 2016 update (
http://www.rabieschallengefund.org/l...hallenge-trial ):
"Fifteen dogs were included in this trial. Only one of the 5 dogs vaccinated in 2007 showed protection against rabies, while 4 of 5 dogs vaccinated in 2009 (80%) demonstrated protection against a rabies virus challenge. Once all 5 of the unvaccinated control dogs showed the very early clinical signs of rabies virus infection, they were humanely euthanized.
Per CFR’s Title 9 recommendations, the surviving 5 vaccinates will remain under observation for another 6 weeks to detect late development of any clinical signs of rabies."
So the vaccination failed after nine years, but was 80% effective after 7 years. Unfortunately, this brief report does not give the titer values, although it mentions that these data were collected.