This study investigates human blockage with variations in antenna half-power beamwidth (HPBW) through an effective numerical method and a high-resolution human voxel model. The whole-body voxel model of Japanese adult males, considering detailed configuration of inner tissues and higher resolution of 1 mm, was employed. The electromagnetic field distribution of a radiated antenna towards human body was reconstructed based the plane wave spectrum expansion (PWS) method, which is hybridized with the finite-difference time-domain (FDTD) method to obtain the total electromagnetic field absorption power ($P_{\text{ab}}$) by the human body at 28 GHz. The impact on human blockage caused by different antenna HPBWs, as well as their separation distance, was investigated. The results indicate that when the antenna radiation beam is directed towards the lower back of the human body, a 15-dB variation in $P_{\text{ab}}$ is observed when changing the separation distance from 1 to 5 m. Above 5 m, $P_{\text{ab}}$ is almost independent of antenna HPBW. A mean value based fitting curve suggest that human blockage increases slightly with a reduction in the antenna HPBW. The variation range of $P_{\text{ab}}$ agrees well with field measurement campaign from a previous study, indicating the effectiveness of the hybrid simulation method. The findings provide a practical approach for human blockage analysis when designing wireless communication systems in dense urban environments at millimeter wave frequencies.