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. 2022 Sep 28;13(1):5701.
doi: 10.1038/s41467-022-33076-4.

Effect of booster vaccination against Delta and Omicron SARS-CoV-2 variants in Iceland

Gudmundur L Norddahl #  1 , Pall Melsted #  1   2 , Kristbjorg Gunnarsdottir  1 , Gisli H Halldorsson  1 , Thorunn A Olafsdottir  1 , Arnaldur Gylfason  1 , Mar Kristjansson  3 , Olafur T Magnusson  1 , Patrick Sulem  1 , Daniel F Gudbjartsson  1   2 , Unnur Thorsteinsdottir  1   4 , Ingileif Jonsdottir  1   4 , Kari Stefansson  5   6
Affiliations

Effect of booster vaccination against Delta and Omicron SARS-CoV-2 variants in Iceland

Gudmundur L Norddahl et al. Nat Commun. .

Abstract

By the end of July 2021, the majority of the Icelandic population had received vaccination against COVID-19. In mid-July a wave of SARS-CoV-2 infections, dominated by the Delta variant, spread through the population, followed by an Omicron wave in December. A booster vaccination campaign was initiated to curb the spread of the virus. We estimate the risk of infection for different vaccine combinations using vaccination data from 276,028 persons and 963,557 qPCR tests for 277,687 persons. We measure anti-Spike-RBD antibody levels and ACE2-Spike binding inhibitory activity in 371 persons who received one of four recommended vaccination schedules with or without an mRNA vaccine booster. Overall, we find different antibody levels and inhibitory activity in recommended vaccination schedules, reflected in the observed risk of SARS-CoV-2 infections. We observe an increased protection following mRNA boosters, against both Omicron and Delta variant infections, although BNT162b2 boosters provide greater protection against Omicron than mRNA-1273 boosters.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Antibody and inhibition levels by primary vaccination series.
A Schematic overview of the recruited groups used in the study. B Anti-Spike-RBD antibody and ACE2-Spike binding inhibition levels across vaccine groups.
Fig. 2
Fig. 2. Groups used in the study of the effect of booster vaccination in persons vaccinated with Ad26.COV2.S.
A schematic overview of the recruited groups.
Fig. 3
Fig. 3. Effect of mRNA booster vaccination on antibody and inhibition levels.
A Anti-Spike-RBD antibody and ACE2-Spike binding inhibition before and after an mRNA booster in persons vaccinated with Ad26.COV2.S in comparison to two dose BNT162b2 vaccination. B Anti-Spike-RBD antibody levels in persons vaccinated with Ad26.COV2.S before and after an mRNA booster. C ACE2-Spike binding inhibition levels in persons vaccinated with Ad26.COV2.S before and after an mRNA booster.
Fig. 4
Fig. 4. Waning of antibody and inhibitory levels following a booster dose of mRNA-1273.
A Schematic overview of the recruited group used in the study. B Anti-Spike-RBD antibody levels in persons vaccinated with two doses of ChAdOx1 vaccine before and after mRNA-1273 booster vaccination. C ACE2-Spike binding inhibition levels in persons vaccinated with two doses of ChAdOx1 vaccine before and after mRNA-1273 booster vaccination.
Fig. 5
Fig. 5. Retrospective total population study.
Schematic overview of the selection process.
Fig. 6
Fig. 6. Adjusted cumulative hazard rate of SARS-CoV-2 infections.
A–C Infections caused by the Delta variant July 1–November 22, 2021. D–F Infections caused by the Delta variant December 1, 2021–January 8, 2022. G–I Infections caused by the Omicron variant December 1–January 8, 2022. Top row: Recommended vaccine schedules. Middle row: Comparison of mRNA booster vaccination of Ad26.COV2.S recipients with BNT162b2-BNT162b2 as reference. Bottom row: Comparison of three dose vaccination with more than 5000 vaccinees, using BNT162b2-BNT162b2 as reference.
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