Vickers and colleagues analyzed the incidence of pertussis reported to the Saskatoon Regional Health Authority in Saskatchewan between Jan.1, 1995, and Sept. 30, 2005.
They found that children aged less than 1 year or aged between 1 and 4 years who had only received whole-cell pertussis (wP), or a combination of wP and acellular pertussis (aP), had a lower incidence of pertussis than children who had received only aP, whereas a reverse trend was seen in children aged 5-9 years.
They suggest that consideration be given to revisiting the optimal immunization strategy against pertussis.
In a related commentary, Halperin and De Serres note that these findings contradict those from other recent reports and surveillance data collected in Canada. They present reasons for this and support the continued use of the aP vaccine. Pertussis immunization is usually given as part of the "5-in-1" shot (DPTP-Hib) that is routinely administered to children at the ages of 2, 4, 6 and 18 months, and as part of a booster shot (DPTP) given at 4-6 years. Between July 1997 and April 1998, all provinces and territories in Canada switched from using the wP vaccine to using only the aP vaccine. Canada had a high incidence of pertussis, and studies showed that the Canadian wP vaccine introduced in the 1980s had low effectiveness.
p. 1213 Whole-cell and acellular pertussis vaccination programs and rates of pertussis among infants and young children -- David Vickers, Allen G. Ross, Raúl C. Mainar-Jaime, Cordell Neudorf, Syed Shah
http://www.cmaj.ca/pressrelease/pg1213.pdf
p. 1219 Household transmission of SARS, 2003 -- Samantha D. Wilson-Clark, Shelley L. Deeks, Effie Gournis, Karen Hay, Susan Bondy, Erin Kennedy, Ian Johnson, Elizabeth Rea, Theodore Kuschak, Diane Green, Zahid Abbas, Brenda Guarda http://www.cmaj.ca/pressrelease/pg1219.pdf
Journal
Canadian Medical Association Journal