What are the appropriate investigations and management for a 2-year-old child with worsening symptoms of pertussis (whooping cough), despite previous vaccination, and how can the mother be counseled regarding vaccine failure, particularly with a 4-week-old sibling at home?

From the Guidelines

Vaccines are not 100% effective, and even vaccinated children can contract pertussis, but they typically experience less severe symptoms and shorter illness duration compared to unvaccinated children. When counseling the mother about vaccine failure in this situation, I would explain that the DTaP vaccine is about 80-90% effective after completing the primary series, but immunity wanes over time, which is why boosters are needed 1. The 2-year-old likely has a milder case than would have occurred without vaccination.

Key Points to Discuss with the Mother

• The child should receive azithromycin (10 mg/kg on day 1, then 5 mg/kg for 4 more days) to reduce contagiousness, as recommended by the CDC guidelines 1.
• The 4-week-old sibling needs immediate prophylactic antibiotics (same azithromycin regimen) as infants are at highest risk for severe complications.
• The mother should also receive prophylaxis to prevent transmission to the infant sibling.
• I would emphasize that despite this breakthrough infection, vaccines remain the best protection against pertussis and its complications, especially for vulnerable family members like the infant sibling.
• The family should maintain good respiratory hygiene, and the infected child should avoid contact with the infant until completing 5 days of antibiotics, as recommended by the CDC guidelines 1.

Management and Prevention

• The child's symptoms should be monitored closely, and the family should follow up with their healthcare provider to ensure the infection is resolving.
• The family should be educated on the importance of vaccination and the need for boosters to maintain immunity against pertussis 1.
• The mother should be reassured that the vaccine has likely reduced the severity of the illness in her child, and that vaccination is still the best way to protect against pertussis and its complications.

From the Research

Investigations and Management

• The child has been diagnosed with pertussis, and the management should focus on reducing the severity of symptoms and preventing the spread of the disease to the 4-week-old sibling and other contacts.
• According to 2, azithromycin is recommended as the first-line antibiotic for the treatment of pertussis.
• The study in 3 highlights the importance of early diagnosis and treatment with a macrolide antibiotic, such as azithromycin, to mitigate complications and reduce the spread of the disease.
• The management of pertussis should also include measures to prevent the spread of the disease, such as isolating the infected child and ensuring that all contacts are aware of the symptoms and risks of pertussis.

Counseling the Mother

• The mother should be counseled that vaccine failure can occur, and it is possible for a vaccinated child to contract pertussis.
• However, as stated in 4, vaccination can help reduce the severity of symptoms and prevent complications.
• The mother should be reassured that the vaccine is not 100% effective, but it can significantly reduce the risk of severe disease and transmission to others.
• It is essential to explain that the child's vaccination status does not guarantee complete protection against pertussis, but it can help reduce the severity of symptoms and prevent complications.
• The study in 5 suggests that early treatment with antibiotics, such as azithromycin or clarithromycin, can improve clinical symptoms and reduce the duration of coughing.
• The mother should be informed that the 4-week-old sibling is at high risk of contracting pertussis and should be closely monitored for symptoms.
• The mother should also be advised to take measures to prevent the spread of the disease, such as ensuring that all contacts are aware of the symptoms and risks of pertussis and taking steps to isolate the infected child.
• As mentioned in 6, antibiotics are effective in eliminating B. pertussis from patients with the disease, rendering them non-infectious, but do not alter the subsequent clinical course of the illness.