Effect of mass campaigns with full and fractional doses of pneumococcal conjugate vaccine (Pneumosil) on the reduction of nasopharyngeal pneumococcal carriage in Niger
Study design
Cluster-randomized trial
Context
In settings with low Pneumoccocal Conjugate Vaccine (PCV) coverage, mass campaigns targeting multi-age cohorts (MAC) might accelerate herd protection but would be costly. Campaigns using fractional dose PCV would decrease cost and increase access.
Our role
Coordination, study site, clinical trial implementation, data management and analysis
Partners
- African Research Collaboration for Health Limited
- Abdou Moumani University
- London School of Hygiene and Tropical Medicine
Objectives
To evaluate whether a mass vaccination campaign targeting children approximately 1-9 years of age with a single full dose of PCV is superior to the absence of vaccine in reducing the proportion of children who are carriers of vaccine-serotype pneumococci (VT) at 6 months post-campaign,
To evaluate and subsequently to evaluate if a campaign using a single 20% dose of PCV is non-inferior to the full dose campaign.
Methodology
a cluster-randomized trial in Niger to evaluate the effect of a mass campaign targeting children aged 1-9 years on pneumococcal carriage. 63 villages were randomized in a 3:3:1 ratio to receive campaigns with a single full dose of a 10-valent PCV (Pneumosil®), a single 1/5th fractional dose, or no campaign. We conducted two independent carriage surveys among a total of 2268 households 6 months before and 6 months after vaccination, collecting a nasopharyngeal swab from a child aged 1-9 years for culture and serotyping.
Results
Surveys were conducted between December 22, 2021, and 18 March, 2022, and December 12, 2022, and March 9, 2023. The vaccination campaign was June 15August 2, 2022. Participant characteristics were similar between the two surveys and across arms. Pre-vaccination, vaccine-type (VT) carriage was 15.6% in the fulldose arm, 17.9% in the fractional dose arm, and 18.8% in the control arm. Postvaccination, VT carriage was 4.6% in the full-dose arm, 8.0% in the fractional dose arm, and 16.5% in the control arm. In the primary analysis, the risk difference between the full dose and the control arms was-12.0% [-19.0;-5.0], p=0.001, and between the full dose and fractional dose arms it was-3.5% [-5.8;-1.1], meeting the prespecified non-inferiority criterion. Similar results were seen after adjustment for age, vaccine coverage and other factors.
Conclusion / Impact
MAC campaigns had a marked impact on VT carriage and fractional-dose campaigns met non-inferiority criteria.
Studies have suggested that mass vaccination campaigns could accelerate the achievement of herd immunity. However, such campaigns can be costly and limited in terms of the quantity of vaccine available. Fractional doses could facilitate their deployment, but it is especially in humanitarian emergency contexts, where it is necessary to vaccinate displaced populations on a massive scale, that the supply and cost of vaccines represent an obstacle. In such situations, the exceptional use of fractional doses could protect a larger number of children, offering a viable solution.
Funder
EDCTP
