Several variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the causative virus of the coronavirus disease 2019 (COVID-19), have been identified globally. Some of these variants have been described as variants of concern (VoC), which is a term that describes SARS-CoV-2 variants associated with developed transmissibility, enhanced infection severity or variation in clinical condition, and/or reduced effectiveness of public health and social standards or possible diagnostics, vaccines, and therapeutics.
Recently, a team of researchers from Norway conducted a cohort study to understand the risk of hospitalization in patients with either the Delta or Alpha variants of SARS-CoV-2. In their study, which is published on the preprint server bioRxiv*, the authors also estimated the vaccination efficacy in combating both variants.
Study: No difference in risk of hospitalization between reported cases of the SARS-CoV-2 Delta Variant and the Alpha variant in Norway. Image Credit: shutter_o / Shutterstock.com
This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources
About the study
The team conducted a cohort study on laboratory-confirmed cases of COVID-19 in Norway that were diagnosed between May 3, 2021, and August 15, 2021. The risk ratios were calculated and adjusted with 95% confidence intervals (CIs) using multivariable binomial regression. This accounted for variants, vaccination status, demographic characteristics, week of sampling, and underlying comorbidities.
Study findings
In the current study, 7,977 COVID-19 cases were found to be due to the Delta variant, whereas 12,078 of cases were due to the Alpha variant. Taken together, 347 (1.7%) of these cases were required hospitalization. The adjusted risk ratio of hospitalization for the Delta variant as opposed to the Alpha variant was 0.97.
Moreover, partially vaccinated patients had a 72% reduced risk of hospitalization, with fully vaccinated patients having a 76% reduced risk, in contrast to unvaccinated patients. The graph below illustrates the proportion of SARS-CoV-2 cases and the proportion of cases due to the Alpha and Delta variants.
The current study highlights the importance of considering the local epidemiological characteristics into account when trying to analyze the effect that various variants have on the COVID-19 epidemic in multiple settings. These results are illustrative of a growing cohort of COVID-19 cases in a country in which the health system managed well within potential, and where there was powerful vaccination coverage amongst people who were at greater risk of severe COVID-19. Vaccination coverage was also steadily increasing in Norway as Delta superseded the Alpha variant as the dominant variant.
The findings from this cohort study show no difference in the risk of hospitalization for individuals who were infected with the Delta variant as compared to the Alpha variant in Norway. Although these findings are promising, the scientists emphasize that more research from a broad variety of environments is needed to fully understand the relationship between the Delta variant and severe disease.
Data on the protection offered against severe disease are crucial to supervise future vaccination strategies. However, the results from this study and others indicate that partially and fully vaccinated persons are highly protected against hospitalization with COVID-19.
This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources
Journal references:
- Preliminary scientific report.
Veneti, L., Salamanca, B. V., Seppala, E., et al. (2021). No difference in risk of hospitalization between reported cases of the SARS-CoV-2 Delta Variant and the Alpha variant in Norway. medRxiv. doi:10.1101/2021.09.02.21263014. https://www.medrxiv.org/content/10.1101/2021.09.02.21263014v1
- Peer reviewed and published scientific report.
Veneti, Lamprini, Beatriz Valcarcel Salamanca, Elina Seppälä, Jostein Starrfelt, Margrethe Larsdatter Storm, Karoline Bragstad, Olav Hungnes, et al. 2022. “No Difference in Risk of Hospitalization between Reported Cases of the SARS-CoV-2 Delta Variant and Alpha Variant in Norway.” International Journal of Infectious Diseases 115 (February): 178–84. https://doi.org/10.1016/j.ijid.2021.12.321. https://www.ijidonline.com/article/S1201-9712(21)01218-2/fulltext.
Article Revisions
- Apr 12 2023 - The preprint preliminary research paper that this article was based upon was accepted for publication in a peer-reviewed Scientific Journal. This article was edited accordingly to include a link to the final peer-reviewed paper, now shown in the sources section.
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