There was a study published recently that showed how different vaccines decline in effectiveness over time. Interestingly, some vaccines decline in effectiveness quite rapidly (flu shot), while others remain effective much longer. The take away from the study was, 1) we don't really understand why the longevity of some vaccines is better than others and, 2) the efficacy of many vaccines may not be as good as we think they are over time. Get the shot. Call me, I'll "talk you down".