biostudies-literatureUnknown399(10324)Costa Clemens SANIHR Oxford Biomedical Research Centre<h4>Introduction</h4>The inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac, Sinovac) has been widely used in a two-dose schedule. We assessed whether a third dose of the homologous or a different vaccine could boost immune responses.<h4>Methods</h4>RHH-001 is a phase 4, participant masked, two centre, safety and immunogenicity study of Brazilian adults (18 years and older) in São Paulo or Salvador who had received two doses of CoronaVac 6 months previously. The third heterologous dose was of either a recombinant adenoviral vectored vaccine (Ad26.COV2-S, Janssen), an mRNA vaccine (BNT162b2, Pfizer-BioNTech), or a recombinant adenoviral-vectored ChAdOx1 nCoV-19 vaccine (AZD1222, AstraZeneca), compared with a third homologous dose of CoronaVac. Participants were randomly assigned (5:6:5:Lancet (London, England)521-529https://www.ebi.ac.uk/biostudies/studies/S-EPMC8782575biostudies-literatureHeterologous versus homologous COVID-19 booster vaccination in previous recipients of two doses of CoronaVac COVID-19 vaccine in Brazil (RHH-001): a phase 4, non-inferiority, single blind, randomised study.PMC8782575Valliji Zde Nobrega MMDejnirattisai Wde Avila Mendonca RNBittaye MFranco MMCosta Clemens SAClemens RPollard AJBeveridge ALiu XQueiroz Oliveira ISMongkolsapaya JTejpal CSupasa PVernon SWoods Dde Freitas Souza BSRHH-001 study teamRamos Souza AMartins Medrado CLMead GLambe TAley PVoysey MGonzalez IGSPark Jde Moraes Pinto MICantrell LSmith HFelle SScreaton GRAlmeida Mendes AVDavies SMuniz Martins TSanders HEldawi AWeckx Lde Arruda Cordeiro Matos LJSilveira MBVBibi SUlaszewska Mda Guarda SNFSalvador NMabette RFraga MfalseHeterologous versus homologous COVID-19 booster vaccination in previous recipients of two doses of CoronaVac COVID-19 vaccine in Brazil (RHH-001): a phase 4, non-inferiority, single blind, randomised study.<h4>Introduction</h4>The inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac, Sinovac) has been widely used in a two-dose schedule. We assessed whether a third dose of the homologous or a different vaccine could boost immune responses.<h4>Methods</h4>RHH-001 is a phase 4, participant masked, two centre, safety and immunogenicity study of Brazilian adults (18 years and older) in São Paulo or Salvador who had received two doses of CoronaVac 6 months previously. The third heterologous dose was of either a recombinant adenoviral vectored vaccine (Ad26.COV2-S, Janssen), an mRNA vaccine (BNT162b2, Pfizer-BioNTech), or a recombinant adenoviral-vectored ChAdOx1 nCoV-19 vaccine (AZD1222, AstraZeneca), compared with a third homologous dose of CoronaVac. Participants were randomly assigned (5:6:5:2022-01-01T00:00:00Z2022 Feb2025-04-18T13:44:51.24Z2022-02-11T16:04:20.041ZS-EPMC87825753507413610.1016/S0140-6736(22)00094-0