Rate of SARS-CoV-2 Reinfection During an Omicron Wave in Iceland

Eyþórsson, Elías; Runólfsdóttir, Hrafnhildur Linnet; Ingvarsson, Ragnar Freyr; Sigurðsson, Martin I; Pálsson, Runólfur

doi:10.1001/jamanetworkopen.2022.25320

Cited by 55 publications

(48 citation statements)

References 5 publications

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“…Of the 3,470 papers initially retrieved, seven case-control (4, 21-26) and 11 cohort studies (6)(7)(8)(27)(28)(29)(30)(31)(32)(33)(34) were included in the analyses (Supplementary Figure 1 and Supplementary Table 1). Three studies contributed with two dataset (24,27,31), as the same publication provided separate data for healthcare workers and the general population (31), and for Delta and Omicron waves (24,27): this led to a total of 21 datasets that were included in the analyses (Table 1).…”

Section: Resultsmentioning

confidence: 99%

“…The methodological characteristics of the included studies are summarized in Table 2: the selection of the cohort of patients, the ascertainment of the exposure, and the evaluation of the comparability of subjects were adequate in all studies, while 15 out of 18 adequately addressed the items pertaining to outcome assessment and follow-up (length and missing data). Twenty-one datasets including a total of 18,132,192 individuals were included in the overall meta-analysis comparing the risk of SARS-CoV-2 reinfection in vaccinated vs. unvaccinated subjects (Table 3) (4,(6)(7)(8)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34). In 20 out of 21 datasets, the vaccinated subjects were significantly less likely to be reinfected, with a summary OR of 0.47 (95% confidence interval-CI -0.42-0.54) (Figure 1).…”

Section: Resultsmentioning

confidence: 99%

“…However, the potential addictive protection conferred by hybrid immunity, generated by the combination of prior infection and vaccination, as compared to the sole natural immunity, remains to be fully disclosed (4,5). A few population-based studies suggested that reinfection is less likely in vaccinated vs. unvaccinated subjects, but the magnitude of the association varied across studies, which differed for patients' characteristics, exposure risk, type of SARS-CoV-2 vaccine received, definition of reinfection adopted, and extent of measured confounding (4,(6)(7)(8). In a recent meta-analysis, the overall reinfection rate among vaccinated subjects was quantified to be as low as 0.32%, as compared to 0.74% among previously infected, unvaccinated individuals, but these estimates were obtained from raw, unadjusted data (2).…”

Section: Introductionmentioning

confidence: 99%

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COVID-19 vaccines reduce the risk of SARS-CoV-2 reinfection and hospitalization: Meta-analysis

et al. 2022

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The addictive protection against SARS-CoV-2 reinfection conferred by vaccination, as compared to natural immunity alone, remains to be quantified. We thus carried out a meta-analysis to summarize the existing evidence on the association between SARS-CoV-2 vaccination and the risk of reinfection and disease. We searched MedLine, Scopus and preprint repositories up to July 31, 2022, to retrieve cohort or case-control studies comparing the risk of SARS-CoV-2 reinfection or severe/critical COVID-19 among vaccinated vs. unvaccinated subjects, recovered from a primary episode. Data were combined using a generic inverse-variance approach. Eighteen studies, enrolling 18,132,192 individuals, were included. As compared to the unvaccinated, vaccinated subjects showed a significantly lower likelihood of reinfection (summary Odds Ratio—OR: 0.47; 95% CI: 0.42–0.54). Notably, the results did not change up to 12 months of follow-up, by number of vaccine doses, in studies that adjusted for potential confounders, adopting different reinfection definitions, and with different predominant strains. Once reinfected, vaccinated subjects were also significantly less likely to develop a severe disease (OR: 0.45; 95% CI: 0.38–0.54). Although further studies on the long-term persistence of protection, under the challenge of the new circulating variants, are clearly needed, the present meta-analysis provides solid evidence of a stronger protection of hybrid vs. natural immunity, which may persist during Omicron waves and up to 12 months.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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COVID-19 vaccines reduce the risk of SARS-CoV-2 reinfection and hospitalization: Meta-analysis

et al. 2022

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“…In a recent trial conducted in Island, the authors estimated the proportion of persons who became re-infected with SARS-CoV-2 during the Omicron wave. The probability of reinfection increased with time from the initial infection (odds ratio of 18 months vs. 3 months, 1.56; 95% CI, 1.18–2.08) and was higher among persons who had received 2 or more doses compared with 1 dose or less of vaccine (odds ratio, 1.42; 95% CI, 1.13–1.78) [ 167 ].…”

Section: Resultsmentioning

confidence: 99%

SARS-CoV-2—The Role of Natural Immunity: A Narrative Review

Diani

Leonardi²,

Cavezzi

et al. 2022

JCM

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Background: Both natural immunity and vaccine-induced immunity to COVID-19 may be useful to reduce the mortality/morbidity of this disease, but still a lot of controversy exists. Aims: This narrative review analyzes the literature regarding these two immunitary processes and more specifically: (a) the duration of natural immunity; (b) cellular immunity; (c) cross-reactivity; (d) the duration of post-vaccination immune protection; (e) the probability of reinfection and its clinical manifestations in the recovered patients; (f) the comparisons between vaccinated and unvaccinated as to the possible reinfections; (g) the role of hybrid immunity; (h) the effectiveness of natural and vaccine-induced immunity against Omicron variant; (i) the comparative incidence of adverse effects after vaccination in recovered individuals vs. COVID-19-naïve subjects. Material and Methods: through multiple search engines we investigated COVID-19 literature related to the aims of the review, published since April 2020 through July 2022, including also the previous articles pertinent to the investigated topics. Results: nearly 900 studies were collected, and 246 pertinent articles were included. It was highlighted that the vast majority of the individuals after suffering from COVID-19 develop a natural immunity both of cell-mediated and humoral type, which is effective over time and provides protection against both reinfection and serious illness. Vaccine-induced immunity was shown to decay faster than natural immunity. In general, the severity of the symptoms of reinfection is significantly lower than in the primary infection, with a lower degree of hospitalizations (0.06%) and an extremely low mortality. Conclusions: this extensive narrative review regarding a vast number of articles highlighted the valuable protection induced by the natural immunity after COVID-19, which seems comparable or superior to the one induced by anti-SARS-CoV-2 vaccination. Consequently, vaccination of the unvaccinated COVID-19-recovered subjects may not be indicated. Further research is needed in order to: (a) measure the durability of immunity over time; (b) evaluate both the impacts of Omicron BA.5 on vaccinated and healed subjects and the role of hybrid immunity.

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“…In a recent study conducted in Island, the authors estimated the proportion of persons who become re-infected with SARS-CoV-2 during the Omicron wave. The probability of reinfection increased with time from the initial infection (odds ratio of 18 months vs 3 months, 1.56; 95% CI, 1.18-2.08) and was higher among persons who had received 2 or more doses compared with 1 dose or less of vaccine (odds ratio, 1.42; 95% CI, 1.13-1.78) [158].…”

Section: Comparisons Between Vaccinated and Unvaccinated In The Devel...mentioning

confidence: 98%

SARS-CoV-2 - The Role of Natural Immunity: A Narrative Review

Diani¹,

Leonardi²,

Cavezzi³

et al. 2022

Preprint

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Background: Both natural immunity and vaccine-induced immunity to COVID-19 may be useful to reduce the mortality/morbidity of this disease, but still a lot of controversy exists. Aims: This narrative review analyzes the literature about: a) the duration of natural immunity; b) cellular immunity; c) cross-reactivity; d) the duration of post-vaccination immune protection; e) the probability of reinfection and its clinical manifestations in the recovered patients; f) comparisons between vaccinated and unvaccinated in the possible reinfections; g) the role of hybrid immunity; h) the effectiveness of natural and vaccine-induced immunity against Omicron variant; i) comparative incidence of adverse effects after vaccination in recovered individuals vs. COVID-19-naïve subjects. Material and Methods: through multiple search engines we investigated COVID-19 literature related to the aims of the review, published since April 2020 through July 2022, including also the previous articles pertinent to the investigated topics. Results: nearly 900 studies were collected and 238 pertinent articles were included. It was highlighted that the vast majority of individuals after COVID-19 develop a natural immunity both of cell-mediated and humoral type, which is effective over time and provides protection against both reinfection and serious illness. Vaccine-induced immunity was shown to decay faster than natural immunity. In general, the severity of the symptoms of reinfection is significantly lower than in the primary infection, with a lower degree of hospitalizations (0.06%) and an extremely low mortality. Conclusions: this narrative review regarding a vast number of articles highlighted the valuable protection induced by the natural immunity after COVID-19, which seems comparable or superior to the one induced by anti-SARS-CoV-2 vaccination. Vaccination of the unvaccinated COVID-19-recovered subjects may not be indicated. Further research is needed in order to: a) measure the durability of immunity over time; b) evaluate both the impacts of Omicron-5 on vaccinated and healed subjects and of hybrid immunity.

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Rate of SARS-CoV-2 Reinfection During an Omicron Wave in Iceland

Abstract: Author Contributions: Drs Eythorsson and Palsson had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Cited by 55 publications

References 5 publications

COVID-19 vaccines reduce the risk of SARS-CoV-2 reinfection and hospitalization: Meta-analysis

COVID-19 vaccines reduce the risk of SARS-CoV-2 reinfection and hospitalization: Meta-analysis

SARS-CoV-2—The Role of Natural Immunity: A Narrative Review

SARS-CoV-2 - The Role of Natural Immunity: A Narrative Review

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