[Pertussis immunization within three adult populations concerned by cocoon strategy in Île-de-France]

Pertussis is a highly contagious respiratory tract infection with a high morbi-mortality in non or insufficiently immunized infants. Cocoon strategy was implemented in France in 2004 in order to reduce the disease incidence. The main objective of the study was to estimate immunization coverage according to cocoon strategy among eligible adults in three different settings in Île-de-France.

A descriptive survey was carried out by means of the same questionnaire addressed to relatives of children hospitalized in pediatric wards, to adults living under the same roof as children enrolled in nursery school, and to grandparents who consulted general practitioners. The main outcome was pertussis vaccination of the adult before the child reached 6 months of age. Parent's and grandparent's knowledge about pertussis and medical advice received about cocooning were assessed. The statistical analysis searched for determinants of vaccination according to cocoon strategy.

Between August 2014 and March 2015, 383 adults were included within the scope of the survey of whom 250 had a vaccination status that could be verified. Immunization coverage was 59%, 33% and 31% respectively in relatives of children hospitalized in pediatric wards, in adults living with children enrolled in nursery school, and in grandparents who consulted general practitioners offices. In the entire population, knowledge of the risk of pertussis was noted in 60%, 76% and 91% of cases. The main determinant of adequate and documented pertussis vaccination was "having received medical advice" that was present in 54%, 31% and 19% of cases, respectively.

Cocoon strategy implementation has clearly progressed but remains insufficient. Emphasis needs to be placed on physicians' involvement in pertussis vaccination in adults eligible for cocoon strategy.