Recently, 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 Advisory Committee on Immunization Practices (ACIP) recommends (pdf) that children should get 5 doses of DTaP (the vaccine for (diphtheria, tetanus and pertussis), 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
Because of these complications, a baby who becomes infected with pertussis often requires hospitalization. And because of the ACIP recommendations, babies under the age of 2 months are unvaccinated (from pertussis), and are, therefore, at risk from catching the disease.
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 2012 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.
A newly published study has found that having more adolescents vaccinated with Tdap (the version of DTaP for older children and adults) significantly reduced the risk of babies requiring hospitalization for whooping cough. One Tdap vaccination is recommended by the CDC for adolescents 11-18 years of age (preferably at age 11-12 years) and adults 19 and older. Women should receive Tdap during each of their pregnancies (preferably in the third trimester between the 27th and 36th week).
The results of the study, led by Katherine A. Auger, MD, MSc, of the Department of General Pediatrics at Cincinnati Children’s Hospital Medical Center, provides strong evidence that the Tdap recommendations, implemented in 2006, have had a significant effect on lowering hospitalizations of babies because of pertussis.
- By 2011, approximately 78% of adolescents (children between 11 and 18 years old) were vaccinated with Tdap.
- In 2000, the researchers determined that approximately 6 out of 10,000 babies admitted to the hospital had pertussis. Approximately, 4.9% of those admitted to the hospital were either placed on ECMO (essentially, life support for individuals whose heart and lungs can no longer support the patient), were intubated, or died.
- By 2005, the rate had doubled to around 12 out of 10,000 babies.
- After the Tdap recommendations commenced in 2006, the rate of hospitalization dropped to around 3 by 2011, substantially less than the 2005 number.
The authors concluded:
Infection with pertussis can result in life-threatening and sometimes fatal illness for young infants. The implementation of policy for universal vaccination among adolescents against pertussis appears to have been partially effective in decreasing the rates of hospitalization for pertussis among infants. However, the observed rates of infant hospitalization during the peak year of 2010 were no different than expected. Further Tdap vaccination efforts among adolescents, and likely adults as well, are needed to prevent infant hospitalization on a more consistent basis.
For those of you who pay attention, let’s be clear. Whooping cough is a serious disease that can harm and kill. Two-month old babies are unprotected from whooping cough (and older babies still may not be fully protected until the third or fourth vaccination). Creating a cocoon of vaccinated people around these babies saves their lives. Simple enough.
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- Auger KA, Patrick SW, Davis MM. Infant Hospitalizations for Pertussis Before and After Tdap Recommendations for Adolescents. Pediatrics. 20 October 2013. doi: 10.1542/peds.2013-1747. Impact factor: 5.119.
- 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. Impact factor: 5.738.