The most reputable source I could find that touches on pertussis vaccinations and disease spread is http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/uc

The most reputable source I could find that touches on pertussis vaccinations and disease spread is http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm376937.htm http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/uc..., particularly this part: This research suggests that although individuals immunized with an acellular pertussis vaccine may be protected from disease, they may still become infected with the bacteria without always getting sick and are able to spread infection to others, including young infants who are susceptible to pertussis disease. The study, conducted on animals, does not, however, suggest that the vaccine increases rate of disease spread, rather that vaccinated individuals can serve as unaffected and unsuspecting nodes of transmission. This can happen with the acellular type of vaccine, not the whole-cell.