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Pertactin-Negative Pertussis Strains

What Is Pertactin?

Pertussis vaccines are made up of inactivated components of the bacteria. Unlike flu vaccines, pertussis vaccines are not matched to specific strains each year. One of several components of all pertussis vaccines, pertactin is a protein that helps the bacteria attach to the lining of the airways.

A New England Journal of Medicine letter was published in 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. 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, the illness is more likely to be caused by a pertactin-deficient strain. However, current evidence, including a study published in 2016, 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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