Session:

Pneumococcal Mucosal Infections, Interaction with other organisms and Pneumococcal Vaccines

Abstract No.:

19.001

Title:

Carriage of S. pneumoniae and related respiratory pathogens after PCV-7 implementation

Author(s):

E. Sanders; Prof. in Pediatric Immunology and ID, Utrecht/NL

Abstract:

The human nasopharynx is considered the niche from where respiratory infections originate. Several common residents of the nasopharyngeal microbiota, including Streptococcus pneumoniae,Haemophilus influenzae,Moraxella catarrhalis andStaphylococcus aureus,are major contributors to respiratory and invasive disease in childhood, especially in the youngest with their still immature immune system. Colonisation of the upper respiratory tract appears to be a dynamic process of acquisition and elimination of various microbial species, interacting with the host, its maturing immune system and each other.In the Netherlands, we performed a longitudinal randomized controlled trial in 1003 infants investigating the effects of a 2- and 2+1-dose schedule with 7-valent pneumococcal conjugate vaccine (PCV7) on pneumococcal presence and the potential changes in carriage of H. influenzae, M. catarrhalis and S. aureus in children and parents. We found a 60% reduction of PCV7-serotype pneumococci and a concomitant increase of non-vaccine serotypes (in particular serotype 19A) at age 24 months. We  also found a doubled prevalence of S. aureus at age 12 months, which declined in the second year of life and no longer persisted at 24 months of age. No significant shifts in H. influenzae or M. catarrhalis carriage were found.Next, in two cross-sectional follow-up surveillance studies in 11- and 24-month-old children and parents performed 3 and 4.5 years after introduction of 3+1-dose PCV7-schedule in the Dutch NIP, the overall pneumococcal carriage prevalence had remained stable with PCV7-serotype pneumococci virtually absent but substituted by non-PCV7 serotypes. Again, a significantly higher prevalence of S. aureus was found in 11-month-old but not in 24-month-old children. Furthermore, a higher carriage prevalence of H. influenzae in children and parents was observed but  no changes in M. catarrhalis prevalence. Our studies show that vaccine-induced shifts in pneumococcal colonization may influence nasopharyngeal dynamics and the presence of other respiratory pathogens, particularly S. aureus. This may have implications for respiratory and invasive disease and antibiotic treatment. Therefore, monitoring is mandatory.