tetano
Editor, Senior Moderator
Open Forum Infect Dis
. 2022 Sep 7;9(9)
fac449.
doi: 10.1093/ofid/ofac449. eCollection 2022 Sep.
Effectiveness of COVID-19 Vaccines Over Time Prior to Omicron Emergence in Ontario, Canada: Test-Negative Design Study
Hannah Chung[SUP] 1 [/SUP], Peter C Austin[SUP] 1 2 [/SUP], Kevin A Brown[SUP] 1 3 4 [/SUP], Sarah A Buchan[SUP] 1 3 4 5 [/SUP], Deshayne B Fell[SUP] 1 6 7 [/SUP], Cindy Fong[SUP] 1 [/SUP], Jonathan B Gubbay[SUP] 4 [/SUP], Sharifa Nasreen[SUP] 1 [/SUP], Kevin L Schwartz[SUP] 1 3 4 [/SUP], Maria E Sundaram[SUP] 1 8 [/SUP], Mina Tadrous[SUP] 1 9 [/SUP], Kumanan Wilson[SUP] 10 [/SUP], Sarah E Wilson[SUP] 1 3 4 5 [/SUP], Jeffrey C Kwong[SUP] 1 3 4 5 11 12 [/SUP]
Affiliations
Abstract
Background: Waning protection from 2 doses of coronavirus disease 2019 (COVID-19) vaccines led to third dose availability in multiple countries even before the emergence of the Omicron variant.
Methods: We used the test-negative study design to estimate vaccine effectiveness (VE) against any severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, any symptomatic infection, and severe outcomes (COVID-19-related hospitalizations or death) by time since second dose of any combination of BNT162b2, mRNA-1273, and ChAdOx1 between January 11, and November 21, 2021, for subgroups based on patient and vaccine characteristics.
Results: We included 261 360 test-positive cases (of any SARS-CoV-2 lineage) and 2 783 699 individuals as test-negative controls. VE of 2 mRNA vaccine doses decreased from 90% (95% CI, 90%-90%) 7-59 days after the second dose to 75% (95% CI, 72%-78%) after ≥240 days against infection, decreased from 94% (95% CI, 84%-95%) to 87% (95% CI, 85%-89%) against symptomatic infection, and remained stable (98% [95% CI, 97%-98%] to 98% [95% CI, 96%-99%]) against severe outcomes. Similar trends were seen with heterologous ChAdOx1 and mRNA vaccine schedules. VE estimates for dosing intervals <35 days were lower than for longer intervals (eg, VE of 2 mRNA vaccines against symptomatic infection at 120-179 days was 86% [95% CI, 85%-88%] for dosing intervals <35 days, 92% [95% CI, 91%-93%] for 35-55 days, and 91% [95% CI, 90%-92%] for ≥56 days), but when stratified by age group and subperiod, there were no differences between dosing intervals.
Conclusions: Before the emergence of Omicron, VE of any 2-dose primary series, including heterologous schedules and varying dosing intervals, decreased over time against any infection and symptomatic infection but remained high against severe outcomes.
Keywords: COVID-19; SARS-CoV-2; vaccine effectiveness; waning immunity.
. 2022 Sep 7;9(9)
fac449.doi: 10.1093/ofid/ofac449. eCollection 2022 Sep.
Effectiveness of COVID-19 Vaccines Over Time Prior to Omicron Emergence in Ontario, Canada: Test-Negative Design Study
Hannah Chung[SUP] 1 [/SUP], Peter C Austin[SUP] 1 2 [/SUP], Kevin A Brown[SUP] 1 3 4 [/SUP], Sarah A Buchan[SUP] 1 3 4 5 [/SUP], Deshayne B Fell[SUP] 1 6 7 [/SUP], Cindy Fong[SUP] 1 [/SUP], Jonathan B Gubbay[SUP] 4 [/SUP], Sharifa Nasreen[SUP] 1 [/SUP], Kevin L Schwartz[SUP] 1 3 4 [/SUP], Maria E Sundaram[SUP] 1 8 [/SUP], Mina Tadrous[SUP] 1 9 [/SUP], Kumanan Wilson[SUP] 10 [/SUP], Sarah E Wilson[SUP] 1 3 4 5 [/SUP], Jeffrey C Kwong[SUP] 1 3 4 5 11 12 [/SUP]
Affiliations
- PMID: 36147595
- PMCID: PMC9487707
- DOI: 10.1093/ofid/ofac449
Abstract
Background: Waning protection from 2 doses of coronavirus disease 2019 (COVID-19) vaccines led to third dose availability in multiple countries even before the emergence of the Omicron variant.
Methods: We used the test-negative study design to estimate vaccine effectiveness (VE) against any severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, any symptomatic infection, and severe outcomes (COVID-19-related hospitalizations or death) by time since second dose of any combination of BNT162b2, mRNA-1273, and ChAdOx1 between January 11, and November 21, 2021, for subgroups based on patient and vaccine characteristics.
Results: We included 261 360 test-positive cases (of any SARS-CoV-2 lineage) and 2 783 699 individuals as test-negative controls. VE of 2 mRNA vaccine doses decreased from 90% (95% CI, 90%-90%) 7-59 days after the second dose to 75% (95% CI, 72%-78%) after ≥240 days against infection, decreased from 94% (95% CI, 84%-95%) to 87% (95% CI, 85%-89%) against symptomatic infection, and remained stable (98% [95% CI, 97%-98%] to 98% [95% CI, 96%-99%]) against severe outcomes. Similar trends were seen with heterologous ChAdOx1 and mRNA vaccine schedules. VE estimates for dosing intervals <35 days were lower than for longer intervals (eg, VE of 2 mRNA vaccines against symptomatic infection at 120-179 days was 86% [95% CI, 85%-88%] for dosing intervals <35 days, 92% [95% CI, 91%-93%] for 35-55 days, and 91% [95% CI, 90%-92%] for ≥56 days), but when stratified by age group and subperiod, there were no differences between dosing intervals.
Conclusions: Before the emergence of Omicron, VE of any 2-dose primary series, including heterologous schedules and varying dosing intervals, decreased over time against any infection and symptomatic infection but remained high against severe outcomes.
Keywords: COVID-19; SARS-CoV-2; vaccine effectiveness; waning immunity.