Safety and coverage of Pneumosil pneumococcal polysaccharide conjugate vaccine (10-valent PCV) in a camp for internally displaced persons in Somaliland

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INTRODUCTION: Pneumococcal conjugate vaccines (PCVs) have substantially reduced pneumococcal morbidity and mortality worldwide, but their use in crisis settings has been limited. Routine immunisation is typically not feasible during a crisis; however,mass-vaccination campaigns with wider age-targeting could effectively protect crisis-affected populations against pneumococcal disease. The 10-valent Pneumosil PCV (PCV10-SII) is currently licensed for use in children aged 6 weeks to 2 years. We conducted a nested phase II evaluation of PCV10-SII safety within a phase IV intervention study measuring the impact of a PCV campaign on pneumococcal carriage. METHODS: We vaccinated children aged 6 weeks to 59 months in a camp for internally displaced persons (IDPs) in Somaliland. Children aged <1 year received two doses of PCV10-SII; children aged 1 to 4 years received a single dose. We administered an adverse event following immunisation (AEFI) survey on the day of vaccination (to document the occurrence of background AEFI-associated symptoms over the preceding week), and seven days later. We identified severe adverse events (SAEs) using several approaches including daily follow-up with the local health facility. We assessed nutritional status using mid-upper arm circumference. We also calculated campaign coverage, and estimated population coverage. RESULTS: Of the 364 vaccinated children included in the analysis, two (<1 %) were malnourished. AEFIs occurred in 34 (11 %) children after their first dose, and in 20 (49 %) infants after their second dose. The most common AEFIs were fever (n = 36, 10 %), decreased appetite (n = 15, 4 %), and a rash at the injection site (n = 13, 4 %). We detected three SAEs. On investigation, none of the SAEs were deemed to be causally associated with vaccination. Campaign coverage was high (93.4 %), while population coverage reduced to 57.1 % over a two-year period. CONCLUSIONS: Vaccination of children PCV10-SII resulted in a small number of AEFIs. Campaign coverage suggests high acceptability of a newly introduced vaccine amongst IDPs in Somaliland. TRIAL REGISTRATION: NCT04945681.

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