The Vaccine Story
Immunization for pertussis with the whole-cell DTP (diphtheria, tetanus, pertussis) vaccine began in 1948, and the result was a significant and rapid decline in cases of whooping cough. The vaccine utilized an inactivated (killed) Bordatella pertussis bacteria to generate an immune response. A four-dose series was 70 to 90% effective in preventing serious pertussis disease, but the protection waned within 5 to 10 years. Common side effects included local reactions and fever, while less common but more alarming side effects of prolonged crying, temporary loss of muscle tone, and febrile seizures were observed. Use of this vaccine led to extremely low rates of pertussis in the US, less than 5,000 cases per year, during the 1970s. While still used elsewhere, the DTP is no longer available in the United States.
A Better Vaccine?
In an effort to provide immunity with fewer side effects, the DTaP (diphtheria, tetanus, acellular pertussis) vaccine for children was first approved for use in the US in 1991. The DTaP creates immunity with inactivated components of the pertussis bacteria, but it does not contain whole bacteria. It is still given to children throughout the United States and elsewhere. Vaccine side effects, especially severe side effects, are less frequent with the acellular vaccine, and the rates of immunity are around 80 to 90%. Protection from pertussis still wanes by adolescence.
Protecting Young Adults
The Tdap (tetanus, diphtheria, acellular pertussis) vaccine, specially formulated to boost immunity to pertussis in adolescents and adults, was first licensed in 2005. One dose of this vaccine booster produces an immune response similar to the immune response from three doses of the DTaP in infants. Seventy percent of patients will be protected from pertussis following the Tdap.
A study published this month in the Journal of Pediatrics shows that current vaccination strategies may not be effective in creating long-term immunity to pertussis in adolescents. Following the 2010 and 2014 pertussis outbreaks in California, Klein and colleagues analyzed Tdap vaccine effectiveness in Kaiser Permanante Northern California adolescent patients. Patients studied had received only the DTaP and Tdap vaccines. None had received the DTP vaccine. Rates of pertussis infection were compared with overall vaccination rates. The results made headlines, with pertussis immunity decreasing from 68.8% during the first year after Tdap immunization to 8.9% by year four.