Parent "cocoon" immunization to prevent pertussis-related hospitalization in infants: the case of Piemonte in Italy.

Pertussis incidence in Piemonte (Italy) is now at the lowest level ever reached (0.85 per 100,000 in 2010) but the disease is still endemic in infants (54 per 100,000 in 2005-2010). Parental "cocoon" immunization has been proposed in some countries (i.e. United States, France) as a measure to protect newborns from serious pertussis outcomes. We assessed the number needed to vaccinate (NNV) to prevent hospital admissions in infants (<12 months) and the potential cost-effectiveness of this strategy in Piemonte. The NNV for parental immunization was at least 5000 to prevent one infant hospitalization in the latest epidemic cycle (2005-2010) at the cost of >€100,000. The "cocoon" programme leads to net costs from a National Health Service (NHS) perspective (ROI<1). In contexts of low incidence and without reliable data on a high parent-attributable infant risk, the parental "cocoon" programme is poorly efficient and very resource intensive in preventing pertussis in infants.