Evaluation of storing hepatitis B vaccine outside the cold chain in the Solomon Islands: Identifying opportunities and barriers to implementation

Monovalent Hepatitis B vaccine (HepB) is heat stable, making it suitable for storage outside cold chain (OCC) at 37 °C for 1 month. We conducted an OCC project in the Solomon Islands to determine the feasibility of and barriers to national implementation and to evaluate impact on coverage. Healthcare workers at 13 facilities maintained monovalent HepB birth dose (HepB-BD) OCC for up to 28 days over 7 months. Vaccination data were recorded for children born during the project and those born during 7 months before the project. Timely HepB-BD coverage among facility and home births increased from 30% to 68% and from 4% to 24%, respectively. Temperature excursions above 37 °C were rare, but vaccine wastage was high and shortages common. Storing HepB OCC can increase HepB-BD coverage in countries with insufficient cold chain capacity or numerous home births. High vaccine wastage and unreliable vaccine supply must be addressed for successful implementation.