Background. Despite an increase in immunisation coverage rates and number vaccines offered in Zambia over the past decade, the financial sustainability to maintain these gains is uncertain. This paper analyses availability of fiscal space to sustain the immunisation programme in Zambia in the short to medium term. Methods. We assessed fiscal space using a standard framework consisting of five pillars: economic growth, expenditure reprioritisation, grants and loans, earmarking of funds, and efficiency gains on existing outlays. To determine fiscal space from the five sources, we applied various analytical techniques including regression analysis on time series data from 1995-2018, Data Envelopment Analysis on cross section administrative data from a sample of 25 health districts, and benchmarking. Results. The evidence shows that fiscal space for immunisation in Zambia is negligible. Health spending is too weakly related to national income to generate fiscal space from economic growth. Reprioritisation of expenditure is difficult because of the huge burden from sovereign debt. Further, introducing new taxes barely three years after the introduction of a social health insurance tax is politically not feasible. Additionally, grants from donors are erratic and likely to diminish in the medium to long-run. However, fiscal space from efficiency gains is quite substantial. Conclusions. Prospects for increasing funding for immunisation from the five sources of fiscal space are minimal. However, efficiency gains in the immunisation programme can go a long way in freeing up resources. The challenge lies in identifying and resolving the sources of technical inefficiency.