tetano
Editor, Senior Moderator
PLoS One
. 2024 Feb 23;19(2):e0299304.
doi: 10.1371/journal.pone.0299304. eCollection 2024. Protection of prior SARS-CoV-2 infection, COVID-19 boosters, and hybrid immunity against Omicron severe illness: A population-based cohort study of five million residents in Canada
Shishi Wu[SUP] 1 [/SUP], Yanhong Li[SUP] 1 [/SUP], Stefan Baral[SUP] 2 [/SUP], Sharmistha Mishra[SUP] 3 4 5 [/SUP], Maria Koh[SUP] 6 [/SUP], Haley Golding[SUP] 6 [/SUP], Jeffrey C Kwong[SUP] 1 6 7 8 9 10 [/SUP], Xiaolin Wei[SUP] 1 4 6 8 [/SUP]
Affiliations
Background: Evidence on protection of different patterns of infection- and vaccine-acquired immunity against Omicron-associated severe illness is useful in planning booster vaccination strategies. We examined protection of prior SARS-CoV-2 infection, a third or a fourth COVID-19 vaccine dose, and hybrid immunity against Omicron-associated severe illness.
Methods and findings: This population-based cohort study followed five million individuals with at least one SARS-CoV-2 RT-PCR test before November 21, 2021 until an Omicron-associatedhospitalization or death. We used Cox regression models to estimate risks of Omicron-associated hospitalization and a composite severe outcome (hospitalized and death), among individuals with infection- and/or vaccination-acquired immunity. Individuals who were unvaccinated and had no history of a prior infection severed as the reference group. Both adjusted hazard ratios (HR) and corresponding protection (one minus adjusted HR), with 95% confidence intervals (CIs), were reported. Three doses provided 94% (95%CI 93-95) and 93% (95%CI 91-94) protection against Omicron-associated hospitalization at 2-3 and ≥3 months post-vaccination respectively, similar to the protection conferred by three doses and a prior infection (2-3 months: 99%, 95%CI 97-100; ≥3 months: 97%, 95%CI 92-99) and four doses (1 month: 87%, 95%CI 79-92; 1-2 months: 96%, 95%CI 92-98). In individuals ≥65 years old, protection of four doses increased to 95% (95%CI 91-98) at 1-2 months, significantly higher than that of three doses over the follow-up period. Similar results were observed with the composite severe outcome.
Conclusion: At least three antigenic exposures, achieved by vaccination or infection, confers significant protection against Omicron-associated hospitalization and death in all age groups. Our findings support a third dose for the overall population, regardless of prior infection status, and a fourth dose for the elderly to maintain high level of immunity and substantially reduce risk of severe illness at individual level.
. 2024 Feb 23;19(2):e0299304.
doi: 10.1371/journal.pone.0299304. eCollection 2024. Protection of prior SARS-CoV-2 infection, COVID-19 boosters, and hybrid immunity against Omicron severe illness: A population-based cohort study of five million residents in Canada
Shishi Wu[SUP] 1 [/SUP], Yanhong Li[SUP] 1 [/SUP], Stefan Baral[SUP] 2 [/SUP], Sharmistha Mishra[SUP] 3 4 5 [/SUP], Maria Koh[SUP] 6 [/SUP], Haley Golding[SUP] 6 [/SUP], Jeffrey C Kwong[SUP] 1 6 7 8 9 10 [/SUP], Xiaolin Wei[SUP] 1 4 6 8 [/SUP]
Affiliations
- PMID: 38394091
- PMCID: PMC10889649
- DOI: 10.1371/journal.pone.0299304
Background: Evidence on protection of different patterns of infection- and vaccine-acquired immunity against Omicron-associated severe illness is useful in planning booster vaccination strategies. We examined protection of prior SARS-CoV-2 infection, a third or a fourth COVID-19 vaccine dose, and hybrid immunity against Omicron-associated severe illness.
Methods and findings: This population-based cohort study followed five million individuals with at least one SARS-CoV-2 RT-PCR test before November 21, 2021 until an Omicron-associatedhospitalization or death. We used Cox regression models to estimate risks of Omicron-associated hospitalization and a composite severe outcome (hospitalized and death), among individuals with infection- and/or vaccination-acquired immunity. Individuals who were unvaccinated and had no history of a prior infection severed as the reference group. Both adjusted hazard ratios (HR) and corresponding protection (one minus adjusted HR), with 95% confidence intervals (CIs), were reported. Three doses provided 94% (95%CI 93-95) and 93% (95%CI 91-94) protection against Omicron-associated hospitalization at 2-3 and ≥3 months post-vaccination respectively, similar to the protection conferred by three doses and a prior infection (2-3 months: 99%, 95%CI 97-100; ≥3 months: 97%, 95%CI 92-99) and four doses (1 month: 87%, 95%CI 79-92; 1-2 months: 96%, 95%CI 92-98). In individuals ≥65 years old, protection of four doses increased to 95% (95%CI 91-98) at 1-2 months, significantly higher than that of three doses over the follow-up period. Similar results were observed with the composite severe outcome.
Conclusion: At least three antigenic exposures, achieved by vaccination or infection, confers significant protection against Omicron-associated hospitalization and death in all age groups. Our findings support a third dose for the overall population, regardless of prior infection status, and a fourth dose for the elderly to maintain high level of immunity and substantially reduce risk of severe illness at individual level.