The global health crisis precipitated by the COVID-19 pandemic underscored the necessity of swift vaccine development and distribution to curb virus transmission. However, discussions on vaccine acceptance and hesitancy have predominantly focused on pre-vaccination attitudes, often overlooking the significance of post-vaccination experiences in shaping individual and communal attitudes toward vaccines. This oversight is particularly critical among healthcare workers in low- and middle-income countries (LMICs), who play a dual role in combating the pandemic and influencing public vaccine sentiment. Using the theory of planned behavior, this study explores the post-vaccination experiences of healthcare workers in Sierra Leone and assesses how these experiences influence their attitudes toward vaccine safety, efficacy and their advocacy for vaccine uptake within their communities. Employing a qualitative design, the study interviewed 24 healthcare workers, 21 of whom were vaccinated against COVID-19. Semi-structured interviews, conducted in English or Krio, were audio recorded, transcribed verbatim and analyzed using thematic analysis to identify key themes. Three themes were identified: positive vaccination experiences exceeding initial expectations, strong belief in the vaccine’s protective benefits and active roles in vaccine advocacy. Despite initial hesitations due to concerns over potential adverse effects, participants reported no significant issues post-vaccination, fostering trust in vaccine safety and effectiveness. Healthcare workers’ positive post-vaccination experiences significantly bolster their vaccine advocacy, influencing their recommendations to patients, friends, families, colleagues and community members. This study highlights the importance of understanding and leveraging healthcare workers’ experiences to enhance public trust and vaccine uptake, crucial for pandemic response efforts in LMICs.