This study developed a seven-compartment COVID-19-pneumonia model This study develops a seven-compartment COVID-19-pneumonia model to assess the combined effects of pre-variant vaccination and antiviral therapy on transmission and pneumonia progression. The basic reproduction number was derived using the next-generation matrix, while equilibrium, stability, sensitivity, uncertainty, and Laplace-Adomian analyses characterized the dynamics using initial conditions from Osogbo, Nigeria. Vaccination and antiviral therapy jointly reduced infection and pneumonia burden; 60% vaccine protection with 40% antiviral uptake prevented more than 70% of projected pneumonia cases. Transmission, vaccine protection, and antiviral suppression were the dominant parameters. Coordinated deployment can therefore reduce severe disease and support COVID-19 control in resource-constrained settings.