Age and product dependent vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adults in Norway: a national cohort study, July–November 2021
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Abstract
Background
COVID-19 vaccines have been crucial in the pandemic response and understanding changes in vaccines effectiveness is essential to guide vaccine policies. Although the Delta variant is no longer dominant, understanding vaccine effectiveness properties will provide essential knowledge to comprehend the development of the pandemic and estimate potential changes over time.
Methods
In this population-based cohort study, we estimated the vaccine effectiveness of Comirnaty (Pfizer/BioNTech; BNT162b2), Spikevax (Moderna; mRNA-1273), Vaxzevria (AstraZeneca; ChAdOx nCoV-19; AZD1222), or a combination against SARS-CoV-2 infections, hospitalisations, intensive care admissions, and death using Cox proportional hazard models, across different vaccine product regimens and age groups, between 15 July and 31 November 2021 (Delta variant period). Vaccine status is included as a time-varying covariate and all models were adjusted for age, sex, comorbidities, county of residence, country of birth, and living conditions. Data from the entire adult Norwegian population were collated from the National Preparedness Register for COVID-19 (Beredt C19).
Results
The overall adjusted vaccine effectiveness against infection decreased from 81.3% (confidence interval (CI): 80.7 to 81.9) in the first 2 to 9 weeks after receiving a second dose to 8.6% (CI: 4.0 to 13.1) after more than 33 weeks, compared to 98.6% (CI: 97.5 to 99.2) and 66.6% (CI: 57.9 to 73.6) against hospitalisation respectively. After the third dose (booster), the effectiveness was 75.9% (CI: 73.4 to 78.1) against infection and 95.0% (CI: 92.6 to 96.6) against hospitalisation. Spikevax or a combination of mRNA products provided the highest protection, but the vaccine effectiveness decreased with time since vaccination for all vaccine regimens.
Conclusions
Even though the vaccine effectiveness against infection waned over time, all vaccine regimens remained effective against hospitalisation after the second vaccine dose. For all vaccine regimens, a booster facilitated recovery of effectiveness. The results from this support the use of heterologous schedules, increasing flexibility in vaccination policy.
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SciScore for 10.1101/2022.03.29.22273086: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics not detected. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:However, some limitations of register-based data should be considered when interpreting the results. Data in these registries are not collected for the purpose of this study, and therefore the focus on level of detail, error checking and precision in the …
SciScore for 10.1101/2022.03.29.22273086: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics not detected. Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:However, some limitations of register-based data should be considered when interpreting the results. Data in these registries are not collected for the purpose of this study, and therefore the focus on level of detail, error checking and precision in the available data is not guided by the current study, as would be the case for independent data gathering. For instance, while vaccines administered as part of the Norwegian vaccination program should be in our dataset, it is not unlikely that some have received vaccines outside Norway and not reported them to the Norwegian register (SYSVAK). While limitations in register-based data are important caveats – our cohort study encompassing the whole Norwegian adult population indicates that vaccine effectiveness against severe disease is high among vaccinated individuals. Our estimates remain qualitatively the same for protection against infection and severe disease when splitting by age groups, indicating that the confounding effect of factors that are relatively constant within age-groups introduce little bias in our adjusted models. Appropriate prioritisation and planning of vaccine campaigns is integral for combating COVID-19 and is only possible with updated knowledge on vaccine effectiveness of realistic vaccination regimens achieved in large populations. For our study the overall protection (i.e. a weighted mean of vaccine effectiveness over time) increase through the initial period with a peak of right below 60% on the 21st ...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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SciScore for 10.1101/2021.11.12.21266222: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:However, some limitations of register-based data should be considered when interpreting the results. Data in these registries are not gathered for the purpose of this study, and therefore the focus on level of detail, error checking and precision in the available data is not guided by the current study, as would be the case for …
SciScore for 10.1101/2021.11.12.21266222: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:However, some limitations of register-based data should be considered when interpreting the results. Data in these registries are not gathered for the purpose of this study, and therefore the focus on level of detail, error checking and precision in the available data is not guided by the current study, as would be the case for independent data gathering. Also, for the combined registries there can be errors for specific individuals, missing individuals, old data and problems when linking individual data from different registries. For example, we adjusted the model for crowded living conditions, which is data collected in 2019 and will be slightly outdated, especially for the younger age groups. And while vaccines administered as part of the Norwegian vaccination program should be in our dataset, it is not unlikely that some individuals (especially those with close ties to other countries) have received vaccines outside Norway and not reported them to SYSVAK. While changing aspect of disease dynamics leading to bias and limitations in register-based data are important caveats – our cohort study encompassing the whole Norwegian adult population indicates that vaccine effectiveness against severe disease is high among both partially and fully vaccinated individuals. Confounders that could affect our estimates have the highest potential for introducing bias when studying large heterogenous groups. Our estimates remain qualitatively the same for protection against infection and s...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
-