biostudies-literatureRanzani OTMinistry of Economy and Competitiveness | Instituto de Salud Carlos III (Institute of Health Carlos III)5536https://www.ebi.ac.uk/biostudies/studies/S-EPMC9537178biostudies-literatureUnknown13(1)The effectiveness of inactivated vaccines (VE) against symptomatic and severe COVID-19 caused by omicron is unknown. We conducted a nationwide, test-negative, case-control study to estimate VE for homologous and heterologous (BNT162b2) booster doses in adults who received two doses of CoronaVac in Brazil in the Omicron context. Analyzing 1,386,544 matched-pairs, VE against symptomatic disease was 8.6% (95% CI, 5.6-11.5) and 56.8% (95% CI, 56.3-57.3) in the period 8-59 days after receiving a homologous and heterologous booster, respectively. During the same interval, VE against severe Covid-19 was 73.6% (95% CI, 63.9-80.7) and 86.0% (95% CI, 84.5-87.4) after receiving a homologous and heterologous booster, respectively. Waning against severe Covid-19 after 120 days was only observed after a homologous booster. Heterologous booster might be preferable to individuals with completed primary series inactivated vaccine.Nature communicationsEffectiveness of an inactivated Covid-19 vaccine with homologous and heterologous boosters against Omicron in Brazil.PMC9537178Sara Borrell fellowship (CD19/00110)Said RFCDean NECummings DATAndrews JRTsuha DHDavid LCSLind MLCroda Jde Melo RLFernandes CFRRanzani OTde Franca GVAKo AITorres MSSAlmiron MHitchings MDTde Oliveira RDfalseEffectiveness of an inactivated Covid-19 vaccine with homologous and heterologous boosters against Omicron in Brazil.The effectiveness of inactivated vaccines (VE) against symptomatic and severe COVID-19 caused by omicron is unknown. We conducted a nationwide, test-negative, case-control study to estimate VE for homologous and heterologous (BNT162b2) booster doses in adults who received two doses of CoronaVac in Brazil in the Omicron context. Analyzing 1,386,544 matched-pairs, VE against symptomatic disease was 8.6% (95% CI, 5.6-11.5) and 56.8% (95% CI, 56.3-57.3) in the period 8-59 days after receiving a homologous and heterologous booster, respectively. During the same interval, VE against severe Covid-19 was 73.6% (95% CI, 63.9-80.7) and 86.0% (95% CI, 84.5-87.4) after receiving a homologous and heterologous booster, respectively. Waning against severe Covid-19 after 120 days was only observed after a homologous booster. Heterologous booster might be preferable to individuals with completed primary series inactivated vaccine.2022-01-01T00:00:00Z2022 Oct2025-04-18T21:00:10.313Z2025-04-07T08:59:19.376ZS-EPMC95371783620280010.1038/s41467-022-33169-0