Pneumococcal vaccination strategies for crisis affected populations

What did the study set out to achieve?

This study aimed to identify effective and cost-effective pneumococcal vaccination strategies for crisis affected populations. Specifically to:

1. identify optimal mass pneumococcal vaccination strategies that reduce disease burden in displacement, rural and urban crisis scenarios;
2. estimate the cost and cost-effectiveness of these strategies; and
3. quantify the global theoretical pneumococcal vaccine need for humanitarian uses.

The project expected to produce recommendations on optimal pneumococcal vaccination strategies as well as:

• A unique quantification of social mixing and nasopharyngeal carriage patterns in a displaced, overcrowded population, providing a basis for further work on disease control strategies in such populations, including for other pathogens;
• A readily transferable, general model to estimate pneumococcal carriage, disease burden and the potential benefit of vaccination in other crisis settings, helping to tailor strategies and prioritisation decisions to specific contexts.

What were the key findings?

Based on data collected from 509 participants across 464 households (65% of inhabited unique shelters) and 454 swabs, the study found:

• A high prevalence of risk factors for respiratory illness (e.g. crowded living conditions; 20% of children under five years of age were stunted)
• A high disease burden: 46% of children with self-reported recent pneumonia, high crude death rates, and carriage rates similar to those of rural Kenya.
• Vaccination of children under one year of age only has limited and short-lived effects.
• Vaccination of children under five years of age at high coverage can
  • prevent about 30% of severe pneumococcal disease in the 2 years following the campaign
  • partially protect unvaccinated infants for 3-5 years after the campaign due to reduced transmission
• Vaccination of under fives is also cost effective: it prevents a similar amount of disease per dose administered as routine use in infants in Kenya.
• If migration rates are high or vaccine coverage is low, extending campaigns to older children can retain indirect protection.

What are the implications for practitioners and policymakers?

These findings imply that humanitarian actors should consider integrating pneumococcal conjugate vaccine campaigns for at least <5-yearold children into their routine humanitarian response portfolio.

This could be done through co-administration with measles containing vaccines and Vitamin A in the acute phase of a humanitarian crisis.

To have the most impact, a PCV campaign should target not only the children most at risk of severe disease (those under two) but also key transmitters (mainly older children aged two to 10). Campaigns limited to only children most at risk are less effective and less efficient in offering durable protection.

The study team are continuing to engage key stakeholders with these messages to influence the guidance for PCV vaccination in humanitarian settings.