Wednesday, March 16, 2016
Are cases of whooping cough an under-vaccination problem?
A New England Journal of Medicine letter was published on February 7, 2013, noting the first appearance in the United States of pertussis strains that are missing pertactin. More recently a paper evaluating the prevalence of these pertactin-deficient strains in the United States was published in Clinical Vaccine Immunology.
Pertactin is one of several components of all pertussis vaccines. It is a protein that helps pertussis bacteria attach to the lining of the airways. There is a new study that found the likelihood of having reported pertussis caused by pertactin-deficient pertussis compared to pertactin-producing pertussis is greater is vaccinated persons. However, current evidence suggests pertussis vaccines continue to prevent disease caused by both pertactin-positive and pertactin-negative pertussis strains since other components of the vaccines provide protection.
CDC is currently conducting studies in the United States to determine whether pertactin deficiency is one of the factors contributing to the increase in the number of reported pertussis cases. CDC will continue to closely monitor the situation and evaluate all available scientific evidence before drawing any conclusions. There is also no suggestion that these new strains are causing more severe cases of pertussis.
Protection from childhood pertussis vaccines still appears to be excellent during the first few years after vaccination, but wears off over time. Outbreaks and epidemics being seen around the country are consistent with what is seen as vaccine protection wears off. It is most likely that the change in pertussis vaccines (from whole cell to acellular in the 1990s) along with better diagnostics and increased reporting are driving the resurgence of pertussis throughout the United States.
Vaccines are the safest and most effective tool we have for preventing pertussis. And we continue to have evidence that pertussis vaccines are working, no longer seeing 200,000 cases per year as we did in the pre-vaccine era.
Note: Antibiotics routinely recommended to treat pertussis remain effective. This new strain is not antibiotic-resistant.
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