MedicalResearch.com Interview with: Dr. Kevin Schwartz, MD MSc Infection Prevention and Control Physician Infection Prevention and Control Public Health Ontario | Santé publique Ontario MedicalResearch.com: What is the background for this study? Response: There has been a resurgence of pertussis, or ‘whooping cough’, in several countries and regions since the introduction of the new “acellular” pertussis vaccine in the 1990s to replace the older “whole cell” vaccine. In Ontario, we have not seen large increases but observed a small outbreak in 2012 that affected both unvaccinated people, as well as in those who have been vaccinated against pertussis. Our objective was to evaluate the effectiveness of the current acellular vaccine used in Ontario. We wanted to find out whether immunity wanes with time in the same way as had been previously observed during a large outbreak in California. We also wanted to study the impact of receiving the older ‘whole cell’ vaccine, which we used in Ontario until 1997.