Multiple drugsSerum sickness-like reaction and rebound effect: case report A 43-year-old woman developed serum sickness-like reaction (SSLR) following immunisation with sars-cov-2-vaccineinactivated-sinovac-biotech against COVID-19. Additionally, she experienced rebound of SSLR following tapering of colchicine, prednisolone, unspecified antihistamines and unspecified steroid for SSLR [not all routes, dosages and durations of treatments to reactions onsets stated].The woman received the first dose of sars-cov-2-vaccine-inactivated-sinovac-biotech [CoronaVac; inactivated COVID19 vaccine]. However, 4 days after receiving the first dose, she presented with pruritic blanchable erythematous macules and patches and excoriated papules and plaques on her trunk and extremities, with post-inflammatory hyperpigmentation. Some lesions showed a feature resembling reticulate erythema. The rashes started as a single patch on the chest and became generalised within 9 days and appeared randomly and did not follow a pattern of centrifugal distribution. The rashes were accompanied by fever, generalised malaise, severe myalgia, arthralgia and cervical lymphadenopathy. Various laboratory tests and investigations were performed. The overall clinical presentation, the temporal relationship with the sars-cov-2-vaccine-inactivated-sinovac-biotech, together with the normal complement levels, favored the diagnosis of sars-cov-2-vaccine-inactivated-sinovac-biotech-related SSLR.The woman was treated with high-dose oral prednisolone 1 mg/kg daily, colchicine 1.2mg daily, antihistamines and a moderatepotency topical steroid [drugs not specified]. She achieved rapid improvement of her condition in less than a week. Thus, a 2 week taper of all treatment drugs was attempted; however, the symptoms recurred with this tapering regimen [rebound effect]. Therefore, prednisolone was reintroduced at 15mg daily with gradual tapering guided by erythrocyte sedimentation rate levels. After 2 months of treatment, inflammatory markers normalised, allowing a slow withdrawal of prednisolone treatment while other drugs were continued. Due of the prolonged course and severity of the illness, further vaccine doses were canceled. The SSLR was reported to the vaccine adverse event reporting system.