Bordatella pertussis, the bacteria that causes whooping cough, is a tricky little bugger. The last few years have seen a Pertussis resurgence and 
California has currently declared an epidemic. Just the name strikes fear into the the hearts of parents with newborns, as infants under 6 months of age are particularly at risk of severe complications from pertussis. “But the pertussis vaccine has been around for decades,” you might protest, “how is it possible that the disease has returned at epidemic levels?” Well, as I said, pertussis is a tricky disease.
For starters, B. pertussis has at least three virulence factors and 5 toxins that it releases. The virulence factors act to help the bacterium stick to respiratory tissue regardless of a dislodging cough. The toxins act to kill respiratory cells and drastically slow down the immune response. In a healthy child or adult, this causes mild to severe coughing with spasms, which can last a very long time before the body is able to get the infection under control. In an infant, severe complications (pneumonia, seizures, failure to thrive, etc.) can arise because of underdeveloped respiratory and immune systems. Pharmaceutical treatment of pertussis is of limited effectiveness since taking an antibiotic will only help lessen the disease if started prior to the onset of coughing, or when the disease looks just like any other cold. Antibiotics are still recommended once a person has started coughing, as they may help reduce the spread of disease to close contacts. (1) The current vaccine, which is acellular (aP, as in part of the DTaP), targets the aforementioned virulence factors. The old vaccine, made of the whole pertussis cell (wP), was more effective but caused many more serious side effects. The current vaccine is much safer, but significantly less effective, which may be one of the main reasons for the current epidemic.
As of June, there were 4,558 confirmed cases of pertussis reported to the California Public Health Department (CDPH). 142 cases required hospitalization and 89 of these were infants under 4 months. One 2-month old infant has died from the disease. Of those cases that had known vaccination history (2,710), only 9% were unvaccinated for the disease. (2) Herein lies the current problem of this epidemic. The aP vaccine is not helping to prevent the majority of current cases of pertussis. The vaccine does not achieve long-lasting immunity and protection wanes by as much as 36% per year after completion of 5 DTaP doses. (3) A recent review article by Chiappini et al. assessed different methods of preventing pertussis with vaccination. It found that with the aP vaccine, multiple strategies need to be used. Specifically, it recommended that newborns be “cocooned” by giving boosters to all people in close contact with the baby and that all adults and adolescents receive booster shots. Preliminary data suggests that vaccinating pregnant women in their third trimester may give additional protection to the newborn during the first few weeks, although there is limited data on the clinical effectiveness of this approach. (4)
It gets more complicated. Recent reports have found that some current B. pertussis strains do not have one of the proteins that is targeted in the vaccine showing evidence of vaccine resistance through change in genetic expression in the DNA. This is the first researchers have seen “vaccine-resistant pertussis.” Furthermore, B. parapertussis is another related bacteria in the Bordatella family that causes whooping cough either alone or as a co-infection with B. pertussis. A 2010 study by Long et al. showed that the aP vaccine not only is ineffective against B. parapertussis but it actually increased colonization by 40 times in mice infected with both pertussis and parapertussis (5). It is possible that this current whooping cough epidemic is actually being facilitated, in part, by widespread use of the aP vaccine.
Parents and public health workers alike are in a pickle. How to protect infants against this disease if the vaccine, modern conventional medicine’s best agent of disease prevention, doesn’t really work? Researchers are scrambling to produce a more effective pertussis vaccine. I argue that true prevention includes a holistic approach looking at maternal and child diet, immune function, respiratory susceptibility, individual constitution and, of course, the tried-and-true, hand-washing.
References:
- Bocka J et. al. Pertussis. Medscape. 2014. Available at: http://emedicine.medscape.com/article/967268-overview
- Annon. Pertussis Report. CDPH. 2014. Available at: http://www.cdph.ca.gov/
programs/immunize/Documents/ Pertussis_Report_6-24-2014.pdf - Yin S. Effectiveness of DTaP wanes over time. Medscape Medical News. Available at: http://www.medscape.com/viewarticle/743026
- Chiappini E et al. Pertussis re-emergence in a post-vaccination era. BMC Infect Dis. 2013; 13:151. Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3623740/
- Long et al. Acellular pertussis vaccination facilitates Bordatella parapertussis infection in a rodent model of bordetellosis. Proc Biol Sci. 2010 Jul 7;277(1690):2017-25.
