Srugo I, Benilevi D, Madeb R, Shapiro S, Shohat T, Somekh E, Rimmar Y, Gershtein V, Gershtein R, Marva E, Lahat N. Pertussis infection in fully vaccinated children in day-care centers, Israel. Emerg Infect Dis. 2000 Sep-Oct;6(5):526-9.

We tested 46 fully vaccinated children in two day-care centers in Israel who were exposed to a fatal case of pertussis infection. Only two of five children who tested positive for Bordetella pertussis met the World health Organization's case definition for pertussis. Vaccinated children may be asymptomatic reservoirs for infection.

This paper indicates that vaccinated children appear to be major resevoirs for infection.