Pertactin-Deficient Pertussis Strains

What Is Pertactin?

Inactivated components of pertussis bacteria make up pertussis vaccines. Unlike flu vaccines, scientists do not match pertussis vaccines 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.

Pertussis vaccines are effective at protecting against disease caused by bacterial strains that are and are not missing pertactin. CDC continues to monitor circulating pertussis strains to determine what impact, if any, molecular changes are having on public health.

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. 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 (i.e., “pertactin-deficient”).1 In 2014, Clinical Vaccine Immunology published a paper evaluating the prevalence of these pertactin-deficient strains in the United States.2 Many other countries have also seen an increase in pertussis caused by pertactin- deficient strains.

One study published in 2015 found if a vaccinated person gets pertussis, a pertactin-deficient strain is more likely to be the cause.3 However, evidence from several other studies continues to show that pertussis vaccines are effective at protecting against disease. Pertactin-deficiency was common in some studies4, 5 looking at the effectiveness of pertussis vaccines and uncommon in other studies.6 In spite of those differences, the studies showed similar vaccine effectiveness, likely because other vaccine components continue to provide protection.

Importantly, there is no suggestion that these new strains cause more severe cases of pertussis. 3

CDC will continue to evaluate all scientific evidence as it becomes available to determine what impact, if any, molecular changes in the pertussis organism are having on public health.

Protection provided by childhood pertussis vaccines still appears to be excellent during the first few years after vaccination. That protection wears off over time though. 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. 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.


1 Queenan AM, Cassiday PK, Evangelista A. Pertactin-negative variants of Bordetella pertussis in the United StatesExternal. N Eng J Med. 2013;368:583–4.

2 Pawloski LC, Queenan AM, Cassiday PK, et al. Prevalence and molecular characterization of pertactin-deficient Bordetella pertussis in the US.External Clin Vaccine Immunol. 2014;21:119–25.

3 Martin SW, Pawloski L, Williams M, et al. Pertactin-negative B. pertussis strains: evidence for a possible selective advantageExternal. Clin Infect Dis. 2015;60(2):223–7.

4 Breakwell L, Kelso P, Finley C, et al. Pertussis vaccine effectiveness in the setting of pertactin-deficient pertussisExternal. Pediatrics. 2016;137(5):e20153973.

5 Acosta AM, DeBolt C, Tasslimi A, et al. Tdap vaccine effectiveness in adolescents during the 2012 Washington state pertussis epidemicExternal. Pediatrics. 2015;135:981–9.

6 Misegades LK, Winter K, Harriman K, et al. Association of childhood pertussis with receipt of 5 doses of pertussis vaccine by time since last vaccine dose, California, 2010External. JAMA. 2012;308:2126–32.