Risk of SARS-CoV-2 reinfection and COVID-19 hospitalisation in individuals with natural and hybrid immunity: a retrospective, total population cohort study in Sweden

Nordström, Peter; Ballin, Marcel; Nordström, Anna

doi:10.1016/s1473-3099(22)00143-8

Cited by 228 publications

(217 citation statements)

References 29 publications

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“…Epidemiological studies conducted during the pre-Omicron period showed prior infection (without vaccination) reduced the risk of reinfection due to the same or different variants by 80-100%, with minimal waning after one year. [14][15][16][17][18] Few studies have quantified prior infection-induced protection against Omicron, but our findings seem consistent with those available. In Qatar, prior infection was 56% effective against Omicron reinfection and 88% against hospitalization, comparable against re-infection at 3-8 (64%) and ≥15 months (60%) postinfection.…”

Section: Discussionsupporting

confidence: 90%

“…14 In Sweden, one-and two-dose hybrid protection reduced the pre-Omicron re-infection risk by 58% and 66%, persisting up to 9 months for the latter, compared to unvaccinated, previously-infected individuals. 16 Perhaps not unexpectedly, we found prior infection improved vaccine protection, and vice-versa, during the Omicron period, consistent with the albeit limited epidemiological evidence elsewhere pertaining to hybrid protection against Omicron 20,34,37 . Among previously-infected HCWs in the United States (US), twodose mRNA vaccination reduced the risk of symptomatic Omicron re-infection by 64% relative to the once or never-vaccinated (combined grouping), similar to our two-dose estimate of 68% instead relative to the infection-naïve nevervaccinated.…”

Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 99%

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Protection against Omicron re-infection conferred by prior heterologous SARS-CoV-2 infection, with and without mRNA vaccination

Carazo

Skowronski

Brisson

et al. 2022

Preprint

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ImportanceOmicron is phylogenetically- and antigenically-distinct from earlier SARS-CoV-2 variants and the original vaccine strain. Protection conferred by prior SARS-CoV-2 infection against Omicron re-infection, and the added value of vaccination, require quantification.ObjectiveTo estimate protection against Omicron re-infection and hospitalization conferred by prior heterologous SARS-CoV-2 (non-Omicron) infection and/or up to three doses of (ancestral, Wuhan-like) mRNA vaccine.DesignTest-negative study between December 26 (epi-week 52), 2021 and March 12 (epi-week 10), 2022.SettingPopulation-based, province of Quebec, CanadaParticipantsCommunity-dwelling ≥12-year-olds tested for SARS-CoV-2.ExposuresPrior laboratory-confirmed infection with/without mRNA vaccination.OutcomesLaboratory-confirmed SARS-CoV-2 re-infection and hospitalization, presumed Omicron by genomic surveillance. The odds of prior non-Omicron infection with/without vaccination were compared among Omicron cases/hospitalizations versus test-negative controls (single randomly-selected per individual). Adjusted odds ratios controlled for age, sex, testing-indication and epi-week. Analyses were stratified by severity and time since last non-Omicron infection or vaccine dose.ResultsWithout vaccination, prior non-Omicron infection reduced the Omicron re-infection risk by 44% (95%CI:38-48), decreasing from 66% (95%CI:57-73) at 3-5 months to 35% (95%CI:21-47) at 9-11 months post-infection and <30% thereafter. The more severe the prior infection, the greater the risk reduction: 8% (95%CI:17-28), 43% (95%CI:37-49) and 68% (95%CI:51-80) for prior asymptomatic, symptomatic ambulatory or hospitalized infections. mRNA vaccine effectiveness against Omicron infection was consistently significantly higher among previously-infected vs. non-infected individuals at 65% (95%CI:63-67) vs. 20% (95%CI:16-24) for one-dose; 68% (95%CI:67-70) vs. 42% (95%CI:41-44) for two doses; and 83% (95%CI:81-84) vs. 73% (95%CI:72-73) for three doses.Infection-induced protection against Omicron hospitalization was 81% (95%CI: 66-89) increasing to 86% (95%CI:77-99) with one, 94% (95%CI:91-96) with two and 97%(95%CI:94-99) with three mRNA vaccine doses. Two-dose effectiveness against hospitalization among previously-infected individuals did not wane across 11 months and did not significantly differ from three-dose effectiveness despite longer follow-up (median 158 and 27 days, respectively).Conclusions and relevancePrior heterologous SARS-CoV-2 infection provided substantial and sustained protection against Omicron hospitalization, greatest among those also vaccinated. In the context of program goals to prevent severe outcomes and preserve healthcare system capacity, >2 doses of ancestral Wuhan-like vaccine may be of marginal incremental value to previously-infected individuals.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 86%

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Protection against Omicron re-infection conferred by prior heterologous SARS-CoV-2 infection, with and without mRNA vaccination

Carazo

Skowronski

Brisson

et al. 2022

Preprint

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“…Previous studies, conducted prior to the Omicron epidemic wave, found that primary vaccination (two doses) afforded protection against reinfection beyond that provided by a prior infection [6][7][8][9] and that a booster dose significantly increase such protection. 10 In contrast, Shrestha et al found that primary vaccination did not provide additional protection (Hazard Ratio, 0.77; 95% CI, 0.53-1.12) against SARS-CoV-2 re-infection among previously infected people during the first month of the Omicron wave.…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of Primary and Booster COVID-19 mRNA Vaccination against Omicron Variant SARS-CoV-2 Infection in People with a Prior SARS-CoV-2 Infection

Lind

Robertson

Silva

et al. 2022

Preprint

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ImportanceThe benefit of primary and booster vaccination in people who experienced prior SARS-CoV-2 infection remains unclear.ObjectiveTo estimate the effectiveness of a primary (two-dose) and booster (third dose) vaccination against Omicron infection among previously infection people.DesignTest-negative case-control study.SettingYale New Haven Health System facilities serving southern Connecticut communities.ParticipantsVaccine eligible people who received SARS-CoV-2 RT-PCR testing between November 1, 2021, and January 31, 2022.ExposureCOVID-19 mRNA primary and booster vaccination.Main Outcomes and MeasuresWe conducted two analyses, each with an outcome of Omicron BA.1 variant infection (S-gene target failure defined) and each stratified by prior SARS-CoV-2 infection status. We estimated the effectiveness of primary vaccination during the period before and during booster eligibility (14-149 and ≥150 days, respectively, after 2nd dose) and of booster vaccination (≥14 days after booster dose). To test whether booster vaccination reduced the risk of infection beyond that of the primary series, we compared the odds among boosted and booster eligible people.ResultsOverall, 10,676 cases and 119,397 controls were included (median age: cases: 35 years, controls: 39 years). Among cases and controls, 6.1% and 7.8% had a prior infection. The effectiveness of primary vaccination 14-149 days after 2nd dose was 36.1% (95% CI, 7.1-56.1%) and 28.5% (95% CI, 20.0-36.2%) for people with and without prior infection, respectively. The effectiveness of booster vaccination was 45.8% (95% CI, 20.0-63.2%) and 56.9% (95% CI, 52.1-61.2%) in people with and without prior infection, respectively. The odds ratio comparing boosted and booster eligible people with prior infection was 0.83 (95% CI, 0.56-1.23), whereas the odds ratio comparing boosted and booster eligible people without prior infection was 0.51 (95% CI, 0.46-0.56).Conclusions and RelevancePrimary vaccination provided significant but limited protection against Omicron BA.1 infection among people with and without prior infection. While booster vaccination was associated with additional protection in people without prior infection, it was not associated with additional protection among people with prior infection. These findings support primary vaccination in people regardless of prior infection status but suggest that infection history should be considered when evaluating the need for booster vaccination.

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“…The mechanism behind this enhanced vaccine efficacy appears to be an expansion of the memory B cell clones present after primary immunization as well as the stimulation of new clones with increased potency and breadth, targeting more conserved areas of the RBD. Moreover, it was shown that in a period dominated by Delta infection, protection was significantly greater in vaccinated (BNT162b2) individuals with evidence of prior infection than those without prior infection 4 , and that protection with one or two doses of vaccine following natural infection was significantly greater than protection associated with natural infection alone 5 .…”

mentioning

confidence: 99%

SARS-CoV-2: from herd immunity to hybrid immunity

Green

2022

Nat Rev Immunol

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Herd immunity, where a pathogen can no longer efficiently spread in a population, is achieved when a large proportion of the population becomes immune, making the spread of infection from person to person unlikely and protecting those without immunity. Despite the global spread of SARS-CoV-2, the failure of virus- and vaccine-induced immunity to prevent transmission, combined with the emergence of antigenically distinct variants, has made herd immunity to SARS-CoV-2 unachievable thus far. Where does this leave us?

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Risk of SARS-CoV-2 reinfection and COVID-19 hospitalisation in individuals with natural and hybrid immunity: a retrospective, total population cohort study in Sweden

Cited by 228 publications

References 29 publications

Protection against Omicron re-infection conferred by prior heterologous SARS-CoV-2 infection, with and without mRNA vaccination

Protection against Omicron re-infection conferred by prior heterologous SARS-CoV-2 infection, with and without mRNA vaccination

Effectiveness of Primary and Booster COVID-19 mRNA Vaccination against Omicron Variant SARS-CoV-2 Infection in People with a Prior SARS-CoV-2 Infection

SARS-CoV-2: from herd immunity to hybrid immunity

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