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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.
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Sin et al. (2009) studied this question.
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