This paper investigates the collective nature of cavity-modified chemical kinetics under vibrational strong coupling (VSC) at finite temperatures and in the presence of a dissipative solvent. The authors develop quantum dynamical methods to treat the dynamics of chemically reacting systems in optical cavities, exploring two simple models to demonstrate how reactivity in the collective VSC regime does not exhibit altered rate behavior in equilibrium but may exhibit resonant cavity modification when the system is explicitly out of equilibrium. The results suggest experimental protocols to modify reactivity in the collective regime and highlight features not included in the models studied, requiring further scrutiny. The study uses the Hierarchical Equations of Motion (HEOM) approach and Multi-Layer Multiconfiguration Time-Dependent Hartree (ML-MCTDH) for simulations, focusing on two model systems: a molecular system with a double-well potential and a proton transfer reaction. The findings indicate that additional molecules coupled to the cavity radiation mode provide additional dissipation, enhancing chemical reactivity in the energy diffusion-limited regime. In the thermodynamic limit, the cavity modification of chemical kinetics vanishes, and the presence of dipole self-energy terms can lead to a suppression of chemical kinetics. The study also explores the importance of initial conditions, showing that non-equilibrium initial conditions can lead to significant modifications in chemical dynamics, while correlated initial conditions result in minimal effects.This paper investigates the collective nature of cavity-modified chemical kinetics under vibrational strong coupling (VSC) at finite temperatures and in the presence of a dissipative solvent. The authors develop quantum dynamical methods to treat the dynamics of chemically reacting systems in optical cavities, exploring two simple models to demonstrate how reactivity in the collective VSC regime does not exhibit altered rate behavior in equilibrium but may exhibit resonant cavity modification when the system is explicitly out of equilibrium. The results suggest experimental protocols to modify reactivity in the collective regime and highlight features not included in the models studied, requiring further scrutiny. The study uses the Hierarchical Equations of Motion (HEOM) approach and Multi-Layer Multiconfiguration Time-Dependent Hartree (ML-MCTDH) for simulations, focusing on two model systems: a molecular system with a double-well potential and a proton transfer reaction. The findings indicate that additional molecules coupled to the cavity radiation mode provide additional dissipation, enhancing chemical reactivity in the energy diffusion-limited regime. In the thermodynamic limit, the cavity modification of chemical kinetics vanishes, and the presence of dipole self-energy terms can lead to a suppression of chemical kinetics. The study also explores the importance of initial conditions, showing that non-equilibrium initial conditions can lead to significant modifications in chemical dynamics, while correlated initial conditions result in minimal effects.