Over the past year or so, there have been several outbreaks of whooping cough (Bordetella pertussis), including one that reached epidemic levels in Washington state, which has been considered one of the worst pertussis outbreaks in the USA during the past several decades. The disease lead to 18 infant deaths in the USA during 2012.
The original DTP vaccine (diphtheria, tetanus and pertussis) became available in the USA in 1948 and was critical to dropping the number of cases of whooping cough from 260,000 in 1934 to less than a few thousand per year in the 1990′s. The Advisory Committee on Immunization Practices (ACIP) recommends (pdf) that children should get 5 doses of DTaP (the replacement for the original DTP vaccine), one dose at each of the following ages: 2, 4, 6, and 15-18 months and 4-6 years. Those children who are not completely vaccinated according to these ACIP recommendations for pertussis are considered to be “undervaccinated.”
- 1 in 4 (23%) get pneumonia (lung infection)
- 1 or 2 in 100 (1.6%) will have convulsions (violent, uncontrolled shaking)
- Two thirds (67%) will have apnea (slowed or stopped breathing)
- 1 in 300 (0.4%) will have encephalopathy (disease of the brain)
- 1 or 2 in 100 (1.6%) will die
Even in adults, there are substantial complications, such as broken ribs from coughing, that can have a significant impact on the overall health of the individual.
One of larger concerns with recent outbreaks of pertussis has been that adults with lapsed immunity or unvaccinated older children may pick up the infection, then pass it to these unvaccinated or partially vaccinated infants (usually less than 1 year old).
In a recently published study, the authors described the benefits of cocooning, a strategy of protecting infants from pertussis by vaccinating those in close contact with them. According to the report, “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.” Alas, the effectiveness of vaccinating the father is probably lower because many fathers have lower amounts of contact with the baby over a period of time compared to the mother, of course.
What we can conclude from their results is that vaccinating mothers is most effective, because they are probably most often in contact with the child. However, siblings could be more in contact with others who might be infected with pertussis, so vaccinating them can be the most effective part of cocooning an infant from pertussis. Of course, if we assume that a family has kept all children up-to-date with vaccinations, then the cocooning strategy is at its strongest without further effort.
The Advisory Committee on Immunization Practices (ACIP) has recommended cocooning with Tdap or DTaP vaccines since 2005 and continues to recommend this strategy for all those with expected close contact with newborns, including family members, caregivers, and friends. ACIP recommends that they get vaccinated at least two weeks before coming into contact with infants. With the increase in pertussis rates, this strategy may be invaluable to protecting the newborn.
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- Bisgard KM, Pascual FB, Ehresmann KR, Miller CA, Cianfrini C, Jennings CE, Rebmann CA, Gabel J, Schauer SL, Lett SM. Infant pertussis: who was the source? Pediatr Infect Dis J. 2004 Nov;23(11):985-9. PubMed PMID: 15545851.
- de Greeff SC, de Melker HE, Westerhof A, Schellekens JF, Mooi FR, van Boven M. Estimation of household transmission rates of pertussis and the effect of cocooning vaccination strategies on infant pertussis. Epidemiology. 2012 Nov;23(6):852-60. doi: 10.1097/EDE.0b013e31826c2b9e. PubMed PMID: 23018969.