With a single vaccination, most does will not get pregnant again in their average lifetime of 5-7 years. In the unlikely event we see a treated doe with a fawn, we will administer a booster shot from a distance without having to recapture her.
On James Island off Sidney, BC, SpayVac was used on the overly abundant fallow deer. It was 100 per cent effective, meaning that after five years the injected deer were still carrying the antibodies that prevent pregnancy and no fawns were born over a six-year period. An experiment in Maple Ridge, BC, with black-tailed does proved similarly successful.