The dynamics and protectiveness of the hybrid immune responses, especially in individuals who have experienced severe COVID-19, remain to be fully understood. This study aims to identify the prevalence and persistence of neutralising antibodies throughout time, and to investigate the longitudinal profile of anti-SARS-CoV-2 IgG antibodies targeting the receptor binding domain (RBD) in patients recovering from severe COVID-19. A total of 42 hospitalised COVID-19 survivors were enrolled from three medical centres in Malaysia. Serial blood samples were collected at four time points post-discharge (approximately 90, 180, 270 and 360 days). IgG titres were quantified using ELISA and neutralising antibodies (NAbs). Statistical analyses were performed to explore antibody dynamics and correlations. Among 42 participants, 24 completed all four visits. Mean antibody titre showed an initial decline after the first visit, followed by a gradual increase over time, with the highest being at Visit 4 (360-390 days post-discharge). The highest titre (266.7 ± 30.9 BAU/mL) was observed in a recipient, 10 days after receiving the fourth vaccination. All participants except one demonstrated protective NAbs at the final visit. Higher BMI was significantly associated with disease severity (P = 0.006), while IgG titres were higher in individuals with more severe initial infections (Category 5). This study highlights the persistence of antibody response with hybrid immunity, with the booster vaccinations contributing to increased antibody titres. RBD-specific IgG titres provide useful insights into their trends, while the concurrent NAbs assessment is important for a comprehensive understanding of the protective efficacy following hybrid immunity.