Abu Sin M, Zenke R, Ronckendorf R, Littmann M, Jorgensen P, Hellenbrand W (2009): Pertussis outbreak in primary and secondary schools in Ludwigslust, Germany demonstrating the role of waning immunity. [Report]
Ped. Infect. Dis. J. 28 (3): 242-244.

A pertussis outbreak primarily affecting school-age children in Ludwigslust, Germany, was investigated in 2006 to estimate attack rates and relative risk of pertussis according to time since last vaccination, after a complete primary course. Results suggested waning immunity beginning approximately 5 years after the last dose of pertussis vaccination. Most cases could have been prevented by earlier booster vaccination.