International Journal of

ADVANCED AND APPLIED SCIENCES

EISSN: 2313-3724, Print ISSN: 2313-626X

Frequency: 12

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 Volume 12, Issue 12 (December 2025), Pages: 19-30

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 Original Research Paper

A beta mixed model approach for analyzing country-level risk and protective factors of COVID-19 death rates in Europe

 Author(s): 

 Nirajan Bam 1, *, Laxmi Prasad Sapkota 2

 Affiliation(s):

  1Department of Mathematical and Physical Sciences, Miami University, Hamilton Campus, Ohio, USA
  2Department of Statistics, Tribhuvan Multiple Campus, Tribhuvan University, Kirtipur, Nepal

 Full text

    Full Text - PDF

 * Corresponding Author. 

   Corresponding author's ORCID profile:  https://orcid.org/0000-0002-9350-6048

 Digital Object Identifier (DOI)

  https://doi.org/10.21833/ijaas.2025.12.003

 Abstract

Although personal health and demographic factors affect COVID-19 death rates, it is also important to examine country-level factors such as healthcare capacity, vaccination coverage, and economic conditions. This study investigates COVID-19 death rates in European countries from January 2020 to August 2023 using a beta mixed-effects model. The main predictors are vaccination rate, gross domestic product (GDP), number of hospital beds, and the share of the population aged 65 and above. The results show that mortality first increases in a linear pattern and then decreases in a quadratic pattern over time. Higher vaccination rates and stronger economies are linked to lower death rates, while a larger elderly population is linked to higher death rates. These findings highlight important national-level risk and protective factors for COVID-19 and offer useful guidance for public health planning and policy decisions.

 © 2025 The Authors. Published by IASE.

 This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/).

 Keywords

 COVID-19 mortality, Vaccination rate, Healthcare capacity, Economic conditions, Elderly population

 Article history

 Received 16 July 2025, Received in revised form 6 November 2025, Accepted 10 November 2025

 Acknowledgment

No Acknowledgment. 

 Compliance with ethical standards

 Conflict of interest: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

 Citation:

 Bam N and Sapkota LP (2025). A beta mixed model approach for analyzing country-level risk and protective factors of COVID-19 death rates in Europe. International Journal of Advanced and Applied Sciences, 12(12): 19-30

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 Figures

  Fig. 1  Fig. 2  Fig. 3  Fig. 4  Fig. 5  Fig. 6  Fig. 7 

 Tables

  Table 1  Table 2  Table 3  

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