Just because we have safe and effective immunizations for vaccine-preventable illnesses doesn’t mean that these vicious bacteria and viruses disappear.  Julie Watson considers pertussis:

A total of 9,935 cases were reported to the California Department of Public Health from Jan. 1 to Nov. 26 — the highest number in 70 years.


Interesting.  The first pertussis vaccine was introduced… 70 years ago!  California is seeing numbers of cases that haven’t been seen since before the pertussis vaccine!  What are the reasons for these concerning statistics?

First, after the modern acellular pertussis vaccine replaced the original whole cell pertussis vaccine in the 1990’s in response to the unacceptable number of side effects, it was discovered that the new vaccine lost it’s effectiveness (immunogenicity) faster. Second, pediatricians, other primary care providers, and emergency departments are more aware of pertussis and consider it more frequently in the differential diagnosis for an infant, child, or adult with a severe (often violent), long-lasting (100 days) cough.  That means that more awareness equals more testing, which results in more diagnosed pertussis.  Finally, there are a minority of parents who refuse these life-saving vaccines for their children and, as we’ve seen previously, they often have California zip codes.  But experts note that most cases of pertussis occur in adequately immunized people:

Dr. Gil Chavez, epidemiologist with the California Department of Public Health, said while more people, especially pregnant women, need to get vaccinated, he does not believe low inoculation rates are the primary cause of the current epidemic: Of this year’s pediatric cases that had information on the child’s vaccination history, only 10 percent of those infected in 2014 had not been vaccinated against pertussis.

Chavez says the new vaccine’s limitations and better tests have led to the increase in cases.


Karen Bardossi breaks down the current pertussis epidemic by age:

Infants aged younger than 1 year had the highest incidence(…) Adolescents aged 15 years had the next highest incidence(…) Overall, the greatest incidence aside from infants occurred in young persons aged 14 to 16 years.

Only 17% of mothers of infants who came down with pertussis during this year’s outbreak had been vaccinated during pregnancy, as recommended by the CDC’s Advisory Committee for Immunization Practices (ACIP). The ACIP recommends that pregnant women receive a tetanus-diphtheria-acellular pertussis (Tdap) booster during the third trimester to protect babies until they can begin immunization at 2 months of age. Recent research has found that vaccinated pregnant women pass antibodies to the fetus through the placenta.


This might be the most disappointing news of all:

Among adolescents who contracted pertussis, only 2.2% had never received pertussis vaccine, and 87% had received Tdap at least 3 years previously, probably indicating waning immunity. The effect of acellular pertussis vaccines wanes more quickly than earlier whole-cell vaccines.


Hopefully some smart scientists are working on a new, safe, and more effective vaccine.