Can a vaccinated individual still contract pertussis (whooping cough)?

Can a Vaccinated Person Contract Pertussis?

Yes, vaccinated individuals can still contract pertussis (whooping cough) because immunity wanes 5-10 years after vaccination, making adolescents and adults susceptible despite childhood immunization. 1, 2

Understanding Pertussis Immunity After Vaccination

• Pertussis vaccination provides significant but not complete protection, as immunity wanes over time after the most recent immunization 2
• Since the early 1980s, despite widespread vaccination, there has been an increase in pertussis incidence across all age groups because:
  • Complete immunization is not protective for all children
  • Many children are incompletely immunized
  • Immunity wanes in most cases 2
• The increase in incidence has been particularly evident in adolescents and adults, with the greatest increase occurring in patients between the ages of 10 and 19 years 2
• Immunity typically wanes 5-10 years after the last pertussis vaccine dose 2, 1

Clinical Presentation in Vaccinated Individuals

• The clinical presentation of pertussis in previously vaccinated individuals is often atypical and milder than in unvaccinated persons 1
• Key differences in vaccinated individuals include:
  • The characteristic "whoop" may be absent 1
  • Symptoms may be less severe but still include persistent cough 2
  • The illness might be mistaken for a common respiratory infection 2
• Despite milder symptoms, vaccinated individuals can still transmit the infection to others, contributing to the reservoir of B. pertussis in the community 2

Diagnostic Considerations

• Pertussis should be suspected when cough lasts ≥2 weeks with paroxysms, post-tussive vomiting, and/or inspiratory whooping, even in vaccinated individuals 1
• Diagnostic testing options include:
  • Nasopharyngeal culture (gold standard) 1
  • PCR testing (faster results but not universally standardized) 1
  • Serologic testing may be helpful in later stages of illness 3
• Pertussis is often overlooked in the differential diagnosis of cough illness, especially in adolescents and adults who may have been vaccinated 1, 2

Prevention and Management

• Current vaccination recommendations include:
  • DTaP primary series for children 1
  • Tdap booster for adolescents 1
  • Tdap for adults up to age 65 1
  • Tdap during each pregnancy between 27-36 weeks' gestation 3
• If pertussis is suspected or confirmed:
  • Macrolide antibiotics (e.g., azithromycin) should be administered early in the course of illness 1
  • Isolation for 5 days from the start of treatment 1
  • Antibiotic prophylaxis for household contacts and high-risk individuals 3

Clinical Implications

• Pertussis remains highly contagious; one active case can infect 70-100% of susceptible household contacts 2
• The secondary attack rate exceeds 80% among susceptible persons 2
• Vaccinated individuals with pertussis can still transmit the infection, which is why "cocooning" (vaccinating close contacts of high-risk individuals) is no longer considered sufficient protection 3
• Pertussis in adults can occasionally present with severe symptoms including cardiac arrhythmia (40%) and syncope (60%) 4

Understanding that vaccination does not confer lifelong immunity to pertussis is essential for clinical suspicion, appropriate diagnosis, and timely treatment to prevent transmission, particularly to vulnerable populations such as unvaccinated infants.