Optimising human rabies vaccine supply chains: A modelling study

Rabies causes thousands of deaths annually in low- and middle-income countries. Despite effective vaccines for post-exposure prophylaxis (PEP), their expense, coupled with supply chain failures, leads to stockouts and preventable deaths. Investment by Gavi, the Vaccine Alliance, aims to improve access to post-exposure vaccines. We evaluate PEP demand in Tanzania and Kenya and examine stock management strategies for improving supply chains in Gavi-eligible countries.

We fitted negative binomial distributions to five years of bite patient data from Tanzania (6646 patients, 20 districts) and Kenya (199,112 patients, 47 counties) to parameterise simulations of post-exposure vaccine demand under WHO-recommended intramuscular (IM) and intradermal (ID) regimens. We compared simulated vaccine use, stockouts, and the impact of stock management strategies across the observed range in demand.

Bite patient incidence varied dramatically; demand surges far exceeded monthly averages (in 6 % of months exceeding 3× average monthly bite patient presentations) and were most extreme in low-incidence settings. ID vaccination reduces vial use by >55 % and reduces stockout risk. Under ID vaccination vial savings are greatest in high-throughput settings, whilst risk mitigation is maximised in low-throughput settings. Decentralizing PEP to more facilities improves access, though reduces vial-sharing opportunities and so increases vial use. Resilient supply chain strategies were identified according to patient throughput, allowing for adaptation to changing demand.

ID vaccination reduces vial use and stockouts, even in low-throughput settings. Tailoring stock management-through adjusted alert thresholds and restocking volumes-can simplify the integration of rabies vaccines into essential immunisation supply chains, improving their availability and preventing unnecessary deaths. However, logistical trade-offs must also be considered.