Background

Interruption of vaccine serotype transmission underlies effectiveness of pneumococcal conjugate vaccine (PCV) programmes at population level. Streptococcus pneumoniae (Sp) nasal carriage density is affected by upper respiratory tract viral infections and PCV. The impact of carriage density on transmission is unknown.

In a multi-centre prospective randomised stepped-wedge trial, we have used the Live Attenuated Influenza Vaccine (LAIV) to modulate Sp carriage density in 2-year-olds and assess impact on household transmission.

Methods

410 families were recruited across 10 UK sites. Families were randomised 1:1 to early or late (4 weeks later) index-child LAIV; saliva and nasopharyngeal samples (NPS) were collected 2-weekly over 2 months. Samples are being analysed for Sp by real-time quantitative PCR (lytA), culture amplification and microarray.

Results

SP nasal carriage rate, densities and density range are highest in our index children (Table 1 for baseline (visit 1) and Figure 1 for visits 1-5).

Conclusions

The range of Sp carriage density is very wide with rates and densities in keeping with the literature. The impact of density on Sp transmission will be analysed when full results are available, June 2020.