Pertactin-Negative Pertussis Strains

The New England Journal of Medicine published a letter in 2013 noting the first appearance in the United States of pertussis strains that are missing pertactin. More recently, Clinical Vaccine Immunology published a paper evaluating the prevalence of these pertactin-deficient strains in the United States. Many other countries have also seen an increase in pertussis caused by pertactin-negative strains.

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 was a study published in 2015 that found that if a vaccinated person gets pertussis, a pertactin-deficient strain is more likely to cause the illness. However, current evidence, including a study published in 2016, suggests pertussis vaccines continue to prevent disease. They continue to prevent disease caused by both pertactin-positive and pertactin-negative pertussis strains since other components of the vaccines provide protection.

CDC is looking into 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. The pertussis outbreaks and epidemics CDC sees around the country are consistent with what researchers see 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. We are 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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