Cocooning, or vaccinating members of a household that are in contact with a person at risk of infection, substantially reduces the disease burden of pertussis in young infants. Because young infants are the most susceptible to pertussis, cocooning with Tdap vaccine has been recommended in the United States by the Advisory Committee on Immunization Practices since 2005.
A recent prospective study in the Netherlands looked at pertussis transmission rates of each family member within each household to determine who was most susceptible to the infection as well as who would be most likely to transmit pertussis to a young child. Researchers looked at 140 households with clinically confirmed cases of pertussis from February 2006 to December 2009 and published their results in the journal Epidemiology
Researchers determined that infants had a 40% chance of contracting whooping cough from their mothers, a 20% chance from their siblings, and only a 15% chance of getting sick from their fathers. They concluded that targeted vaccination of the mother would nearly halve the risk of infection in an infant, whereas selective vaccination of a sibling would be less protective, and vaccination of the father would be the least effective.