Pertussis or whooping cough is caused by the bacteria, Bordetella pertussis. It can infect infants, children and adults alike but is most dangerous in infants less than one year of age. The bacteria adhere to the ciliated epithelial cells that line the upper respiratory tract and release toxins, which damage the cilia causing inflammation and swelling. The disease begins as a benign cold with a runny nose, low-grade fever and mild cough which can progress to paroxysms of many, many coughs followed by a “whoop” which is the characteristic sound of an infant trying to catch his breath. The coughing can be so severe that it can lead to apnea in infants and if not treated can be fatal. As a parent, if you have ever watched and heard your child cough to the point that they are struggling to breathe, it is a completely helpless feeling. In China, pertussis is known as the “100 day cough.”
The best way to prevent pertussis is through vaccination. The “old” vaccine, the DTwP was a whole cell vaccine and had some severe risks that came with it. Persistent, inconsolable crying occurred in one of every 100 doses, fever greater than 105 degrees occurred in one of every 330 doses, and seizures with fever occurred in one of every 1,750 doses. The new vaccine, DTaP, an acellular vaccine, has milder, less serious side effects such as soreness at injection site and mild fever. There has been some debate since the acellular pertussis vaccine was introduced as to the protection it affords and its longevity. In a study published in the June 2013 issue of Pediatrics, “Comparative Effectiveness of Acellular Versus Whole-Cell Pertussis Vaccines in Teenagers,” the researchers concluded that teens who received DTwP vaccines in childhood were more protected during a pertussis outbreak than were those who received DTaP vaccines. Because of this, anyone 11 years or older should receive a booster.
According to a study conducted by pediatric infectious disease physician, Jennifer Vodzak, MD, vaccine-resistant isolates of Bordetella pertussis have appeared in Philadelphia – the first such strains to be seen in the United States. She found that the bacteria had developed two different mutations, each of which deleted their expression of pertactin, an outer membrane protein that helps the bacteria adhere to respiratory epithelium. Pertactin is used as an antigen in the acellular pertussis component of the Tdap vaccine (this is the vaccine given to teens and adults).
According to the CDC, it does not appear that these strains are the reason the United States has experienced a dramatic increase in the number of reported pertussis cases recently, but it will continue to closely monitor the situation before drawing any conclusions. There is also no suggestion that these new strains are causing more severe cases of pertussis. Further research is needed to address these issues.
Even though the immunity offered by the current pertussis vaccine wanes and does not offer herd immunity, vaccination is still highly recommended for all infants with boosters for teens and adults. It is especially important that any adults or children who are in contact with an infant be vaccinated against pertussis.