Effectiveness of COVID-19 mRNA Vaccination in Preventing COVID-19–Associated Hospitalization Among Adults with Previous SARS-CoV-2 Infection — United States, June 2021–February 2022

Plumb, Ian D.; Feldstein, Leora R.; Barkley, Eric; Posner, Alexander B.; Bregman, Howard; Hagen, Melissa Briggs; Gerhart, Jacqueline L.

doi:10.15585/mmwr.mm7115e2

Cited by 87 publications

(77 citation statements)

References 8 publications

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“…Among previously-infected HCWs in the United States (US), two-dose 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 never-vaccinated. 37 Among previously-infected US adults, the Omicron-hospitalization risk was reduced among the vaccinated vs. unvaccinated by 33%, 35% and 68% with one, two and three mRNA doses 38 . The latter is in contrast to our findings showing that among previously-infected people a third dose did not meaningfully improve the already-substantial two-dose protection against Omicron hospitalization (97% vs. 94%), that was furthermore sustained >1 year.…”

Section: Discussionmentioning

confidence: 99%

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: Discussionmentioning

confidence: 99%

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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“…20 A lower VE of two doses COVID-19 mRNA vaccines against hospitalization was also seen in a period dominated by Omicron (34.6%, 95% CI: 25.5% to 42.5%) compared to Delta (47.5%, 95% CI: 38.8% to 54.9%), in a test-negative design study from USA. 21 A major strength of this study is the completeness of the Danish registries, which reduces the risk of selection bias as they cover all individuals residing in Denmark and their contacts with vaccination-or test centers, as well as the Danish personal registration number ensuring individual-level linkage of data. Also, Denmark has had one of the highest testing rates in the world, 22 which limits the risk of undiscovered reinfections.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Vaccine effectiveness against SARS-CoV-2 reinfection during periods of Alpha (B.1.1.7), Delta (B.1.617.2) or Omicron (B.1.1.529) dominance: A Danish nationwide study

Nielsen

Moustsen-Helms

Schelde

et al. 2022

Preprint

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Introduction Individuals with a prior severe acute respiratory corona virus 2 (SARS-CoV-2) infection have a moderate to high degree of protection against reinfection, though seemingly less so when the Omicron variant of SARS-CoV-2 started to circulate. The aim of this study was to evaluate the vaccine effectiveness (VE) against SARS-CoV-2 reinfection, that is, in individuals with prior SARS-CoV-2 infection, during periods with different dominant SARS-CoV-2 variants. Methods A nationwide cohort study design including all individuals with a confirmed SARS-CoV-2 infection, who were alive and residing in Denmark between 1 January 2020 and 31 January 2022 were used. Using Danish nationwide registries, we obtained information on SARS-CoV-2 infections, Coronavirus Disease 2019 (COVID-19) vaccination, age, sex, comorbidity, staying at hospital and region of affiliation. The study population included were individuals with prior SARS-CoV-2 infection. Crude and adjusted estimates of VE against SARS-CoV-2 reinfection with 95% confidence intervals (CIs) were calculated using Poisson and Cox regression models, respectively. The VE estimates were calculated separately for three periods with different dominant SARS-CoV-2 variants (Alpha (B.1.1.7), Delta (B.1.617.2), or Omicron (B.1.1.529)) and by time since vaccination using unvaccinated as the reference. Findings The study population comprised of 209,814 individuals infected before or during the Alpha period, 292,978 before or during the Delta period and 245,530 before or during the Omicron period. Of these, 40,281 individuals had completed their primary vaccination series during the Alpha period (19.2%), 190,026 during the Delta period (64.9%) and 158,563 during the Omicron period (64.6%). VE against reinfection following any COVID-19 vaccine type administered in Denmark, peaked at 85% (95% CI: 37% to 97%) at 104 days or more after vaccination during the Alpha period, 88% (95% CI: 81% to 92%) 14-43 days after vaccination during the Delta period and 60% (95% CI: 58% to 62%) 14-43 days after vaccination during the Omicron period. Waning immunity was observed, and was most pronounced during the Omicron period. Interpretation This study shows that, in previously infected individuals, completing a primary vaccination series was associated with a significant protection against SARS-CoV-2 reinfection compared with no vaccination for all three variant periods. Even though vaccination seems to protect to a lesser degree against reinfection with the Omicron variant, these findings are of public health relevance as they show that previously infected individuals still benefit from COVID-19 vaccination in all three variant periods.

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“…Vaccination remains the safest strategy for preventing complications from SARS-CoV-2 infection, including hospitalization among children and adults ( 4 , 5 ). COVID-19 vaccination following infection provides additional protection against severe disease and hospitalization ( 6 ). Staying up to date ††† with vaccination is recommended for all eligible persons, including those with previous SARS-CoV-2 infection.…”

mentioning

confidence: 99%

Seroprevalence of Infection-Induced SARS-CoV-2 Antibodies — United States, September 2021–February 2022

Clarke¹,

Jones²,

Deng³

et al. 2022

MMWR Morb. Mortal. Wkly. Rep.

252

210

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Effectiveness of COVID-19 mRNA Vaccination in Preventing COVID-19–Associated Hospitalization Among Adults with Previous SARS-CoV-2 Infection — United States, June 2021–February 2022

Cited by 87 publications

References 8 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

Vaccine effectiveness against SARS-CoV-2 reinfection during periods of Alpha (B.1.1.7), Delta (B.1.617.2) or Omicron (B.1.1.529) dominance: A Danish nationwide study

Seroprevalence of Infection-Induced SARS-CoV-2 Antibodies — United States, September 2021–February 2022

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