What are the recommendations for post-exposure prophylaxis (PEP) after whooping cough exposure?

Recommendations for Post-Exposure Prophylaxis After Whooping Cough Exposure

Macrolide antibiotics should be administered as post-exposure prophylaxis (PEP) to close contacts of pertussis cases within 21 days of exposure, with azithromycin being the preferred agent due to better tolerability and shorter treatment duration. 1, 2

Who Should Receive PEP

• PEP should be administered to close contacts of pertussis cases after considering:

  • Infectiousness of the patient and intensity of exposure
  • Potential consequences of severe pertussis in the contact
  • Risk of secondary transmission to high-risk individuals 1

• PEP is strongly recommended for:

  • All household contacts 1
  • Contacts who are at high risk of severe disease:
    • Infants under 12 months (especially those under 4 months) 1
    • Women in the third trimester of pregnancy 1, 2
    • Immunocompromised individuals 2
  • Contacts who may expose high-risk individuals (healthcare workers, childcare workers) 2, 3

Recommended Antimicrobial Agents for PEP

First-line agents:

• Azithromycin (preferred):

  • Adults: 500 mg on day 1, then 250 mg daily for 4 days 1, 2
  • Children: 10 mg/kg on day 1, then 5 mg/kg daily for 4 days 1
  • Infants <1 month: 10 mg/kg daily for 5 days 1

• Clarithromycin:

  • Adults: 500 mg twice daily for 7 days 1
  • Children: 7.5 mg/kg twice daily for 7 days (maximum 500 mg/dose) 1
  • Not recommended for infants <1 month 1

• Erythromycin:

  • Adults: 500 mg four times daily for 14 days 4
  • Children: 40-50 mg/kg/day in 4 divided doses for 14 days (maximum 2g/day) 4
  • Not recommended for infants <1 month due to risk of infantile hypertrophic pyloric stenosis 1

Alternative agent:

• Trimethoprim-sulfamethoxazole (TMP-SMZ):
  • For patients >2 months who cannot tolerate macrolides 1
  • Adults: TMP 8 mg/kg/day, SMZ 40 mg/kg/day in 2 divided doses for 14 days 1
  • Children: Same as adults 1

Timing and Effectiveness of PEP

• PEP should be administered within 21 days of exposure to be effective 1
• PEP aims to eradicate B. pertussis from the nasopharynx of infected persons (symptomatic or asymptomatic) 1
• Short-term antibiotic regimens (azithromycin for 5 days, clarithromycin for 7 days) are as effective as long-term regimens (erythromycin for 14 days) but have fewer side effects 5
• PEP does not alter the clinical course if symptoms have already developed; symptomatic contacts should be treated as cases 1, 5

Special Considerations

• For infants <1 month, azithromycin is the preferred agent due to the association between erythromycin and infantile hypertrophic pyloric stenosis 1
• Pregnant women should receive the same antibiotic regimens as non-pregnant adults 1
• Healthcare workers with known pertussis exposure should either receive PEP or be monitored daily for 21 days and treated at symptom onset 1

Common Pitfalls and Caveats

• Pertussis is highly infectious with a secondary attack rate exceeding 80% among susceptible persons 1
• Patients with pertussis are most infectious during the catarrhal stage and the first 3 weeks after cough onset 1
• Antibiotic prophylaxis does not provide long-term protection; vaccination remains the most important preventive strategy 1
• Recent evidence suggests very high PEP uptake among household contacts, though the effectiveness of PEP in preventing secondary cases in highly vaccinated populations remains unclear 6
• Immunity from vaccination wanes after 5-10 years, making previously vaccinated individuals susceptible to infection 1