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

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.