The startling resurgence of whooping cough infection in the US and UK over the past couple years has scientists perplexed as to the cause. A study published this week in BMC Medicine from researchers at the Santa Fe Institute, in Santa Fe, NM, adds a new hypothesis to the mix: that vaccinated populations do not know they are carriers, and are therefore spreading the infection around the countries.
With 2012 showing the highest rates of whooping cough infection since 1955, researchers developed many hypotheses as to the cause, including waning vaccine effectiveness, bacterial mutation, and rise of the anti-vaccine movement which decreased vaccine coverage. While the authors conclude the latter plays the most significant role, this new study indicates that even when individuals are vaccinated, they may be unwitting carriers and therefore spread the bacteria to hundreds of others over many years.
A main conclusion of the paper states that “cocooning” strategies, in which all family members get vaccinated to prevent newborn infection, may be ineffective. Also, these conclusions mean herd immunity, essentially a “cocooning” strategy for the general population, needs to exceed 99%, a tall order even without the anti-vaccine movement.
The whooping cough vaccine (given as part of the Tdap vaccine) is still vital though for protection from Bordetella pertussis, the causative agent of whooping cough. “It’s the symptoms of pertussis infection that kill people,” paper author and Santa Fe Institute Omidyar Fellow Sam Scarpino says, “and the existing vaccine prevents the most debilitating effects of whooping cough.”
A future goal will be to develop a vaccine that combines the symptom-preventing effects of Tdap with an agent that controls the spread of B. pertussis from person to person. In the meantime, individuals who have been vaccinated should be aware that they may still be contagious, and should take appropriate precautions to protect those that can not be vaccinated.
Edward Marks is a PhD student at the University of Delaware. His research involves the healing of myocardial tissue after major cardiac events using nanomedicine techniques, with the goal of pushing any advancement directly into the clinic. Edward received his BS from Rutgers University and Masters from the University of Delaware.