Proton-boron-11 (p11B) is a nearly aneutronic and naturally abundant fuel, making it a promising candidate for advanced fusion fuels. However, achieving ignition and self-sustaining burn in p11B fuel remains extremely challenging. In comparison to deuterium-tritium (DT) fuel, the fusion reactivity of 11B(p, )2 reaction is significantly lower at plasma temperatures below 100 keV, while radiation losses are substantially higher. As for the additional nonthermal effects, the possibility of an avalanche reaction (or chain reaction) due to suprathermal fusion caused by energetic protons recoiled by p11B fusion-produced α-particles via large-angle elastic scattering has been discussed. Belloni reported that the multiplication factor of -particles G due to suprathermal fusion is at most 1% under the conditions of low ion temperature (Ti–1 keV), high electron temperature (), and electron number density 1024 (Belloni 2021 Plasma Phys. Control. Fusion63 055020). In this study, the -particle multiplication factor due to the suprathermal reaction at higher temperatures was evaluated under the conditions relevant to the ignition and burn processes of p11B fuel in inertial fusion using the latest p11B fusion cross section (Tentori and Belloni 2023 Nucl. Fusion63 086001) and considering the effects of the thermal motion of the background particles. The maximum value of the multiplication factor was found to be only 3% at , , and proton number fraction , indicating that even under such extreme conditions, no avalanche reaction is expected.