Estimation of household transmission rates of pertussis and the effect of cocooning vaccination strategies on infant pertussis.

BACKGROUND

Despite >50 years of universal vaccination, pertussis remains the most prevalent vaccine-preventable infectious disease in developed countries. Pertussis is often mild in adults, but can run a severe course in young infants.

METHODS

Data on transmission of pertussis within households were captured in a population-based, nationwide, prospective study performed in the Netherlands between February 2006 and December 2009. We estimated the transmission rates of pertussis with a clinically confirmed infection in 140 households, using stochastic epidemic models. Parameter estimates were used to gauge the effect of vaccinating household members (cocooning) to prevent the infection in young infants.

RESULTS

Overall transmission rates in the household were high. Fathers were less susceptible than other household members (estimated relative susceptibility of fathers = 0.44 [95% confidence interval (CI) = 0.27-0.72]), whereas mothers may be more infectious to their infants than are other household members (estimated relative infectiousness of mothers = 3.9 [95% CI = 0.59-14]). Targeted vaccination of mothers would approximately halve the probability of infants' infection. Vaccination of siblings is less effective in preventing transmission within the household, but may be as effective overall because siblings more often introduce an infection in the household. Vaccination of fathers is expected to be least effective.

CONCLUSIONS

Selective vaccination of persons in households with a young infant may substantially reduce the disease burden of pertussis in infants by reducing transmission within the household.