  There is considerable interest in predicting the efficiency of Quantum Key
Distribution (QKD) protocols when one of their implementation quantities is
modified. One significant imperfection that affects the efficiency of the setup
is the afterpulse phenomenon which consists in the spontaneous detections
triggered by trapped carriers after previous avalanches at the detectors. While
it is widely studied in bibliography for various QKD protocols, it has been
reported much more scarcely for the well-known decoy-state QKD protocols and
for dual detectors only. We develop a theoretical analysis of afterpulsing
effect on the decoy-state QKD protocols for multiple detectors, delivering
results which can be used as a guide for every practical decoy-state QKD
protocol implementation in real-world deployments. A new formula connecting the
baseline system error rate and the afterpulse probability is derived which may
hold for all protocols as it is consisted of only setup-related quantities.
Numerical simulations addressing the significance of breaking down the
quantities pertaining to the decoy-state QKD protocols are being made, focusing
on the weak+vacuum decoy-state QKD protocol as a characteristic subcase.
