biostudies-literatureGoh YSAgency for Science, Technology and Researche1403https://www.ebi.ac.uk/biostudies/studies/S-EPMC9398778biostudies-literatureUnknown11(8)<h4>Objective</h4>Despite the high vaccine efficacy of mRNA COVID-19 vaccines, there are individuals who developed excessive reactogenic and/or allergic responses after the first mRNA dose and were considered ineligible for further mRNA doses. CoronaVac, an inactivated SARS-CoV-2 vaccine, is recommended in Singapore as an alternative.<h4>Methods</h4>Individuals, ineligible for further mRNA vaccines (BNT162b2 or mRNA-1273) because of excessive reactive responses to prime mRNA vaccination, were recruited and offered two doses of CoronaVac as booster vaccination 38-224 days post their mRNA vaccine dose. Individuals who did not develop any excessive reactive responses after the prime mRNA vaccination were also recruited and given another mRNA vaccine as booster vaccination. Blood samples were Clinical & translational immunologyHeterologous booster vaccination with CoronaVac following prime vaccination with mRNA vaccine.PMC9398778H/20/04/g1/006ACCL/19‐GAP064‐R20H‐HLye DCWong JXEWang CISalleh SNMWang BLim PLZhuo NZPada SNCID Study GroupLim DRXRen ECOng DLSLee ESRouers ANg LFLee RTCTay MZNgoh EZXRenia LSomani JYoung BEChavatte JMLoh CYGoh YSHor PXTan YJChang ZWCOVID‐19 Study GroupMaurer-Stroh SHuang YLeo YSSun LJFong SWLin RTfalseHeterologous booster vaccination with CoronaVac following prime vaccination with mRNA vaccine.<h4>Objective</h4>Despite the high vaccine efficacy of mRNA COVID-19 vaccines, there are individuals who developed excessive reactogenic and/or allergic responses after the first mRNA dose and were considered ineligible for further mRNA doses. CoronaVac, an inactivated SARS-CoV-2 vaccine, is recommended in Singapore as an alternative.<h4>Methods</h4>Individuals, ineligible for further mRNA vaccines (BNT162b2 or mRNA-1273) because of excessive reactive responses to prime mRNA vaccination, were recruited and offered two doses of CoronaVac as booster vaccination 38-224 days post their mRNA vaccine dose. Individuals who did not develop any excessive reactive responses after the prime mRNA vaccination were also recruited and given another mRNA vaccine as booster vaccination. Blood samples were 2022-01-01T00:00:00Z20222025-04-26T19:43:21.825Z2024-11-14T03:43:51.006ZS-EPMC93987783601685210.1002/cti2.1403