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2026 Vol.56, Issue 1 Preview Page

Original Article

Bayesian Analysis of NPI and Vaccination Effects on SARS-CoV-2 Transmission in South Korea 2020–2022
Chaeyeon Yang1
,
Yong Seok Jeong1*
1Department of Biology, Kyung Hee University, Seoul 02447, Republic of Korea
*ysjeong@khu.ac.kr
31 March 2026. pp. 58-72
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Abstract

The relative and combined effects of non-pharmaceutical interventions (NPIs) and vaccination on SARS-CoV-2 transmission remain incompletely quantified, particularly in East Asian settings characterized by high policy compliance. We analyzed the epidemic trajectory in South Korea from May 2020 to July 2022 using a Bayesian hierarchical framework that incorporated variant-weighted transmissibility, NPI stringency indices, vaccine efficacy-adjusted coverage, and humidity as a control variable. Time-varying reproduction numbers were estimated and compared with EpiEstim-derived values for validation. Variant-specific weights were applied to account for shifts from the ancestral strain to Delta and Omicron lineages. Vaccination impact was modeled using product-specific efficacy and coverage proportions to reflect practical transmission reduction. Prior to vaccine rollout, NPIs accounted for a 55.5-77.8% reduction in transmission. Following vaccination initiation in early 2021, NPI effectiveness remained stable (68.6-77.8%), while vaccination effects increased progressively, reaching 54.5% by July 2022. The combined effect of NPIs and vaccination reached 91.7%, substantially exceeding their isolated contributions. Unlike observations in several European countries, NPI effectiveness in South Korea did not markedly decline after vaccine deployment. Humidity exerted a modest seasonal influence, and residual factors showed high uncertainty. Model robustness was confirmed through MCMC convergence diagnostics and PSIS-LOO validation. These findings demonstrate that sustained NPIs and vaccination functioned complementarily rather than competitively in reducing SARS-CoV-2 transmission. The results highlight the importance of integrated public health strategies and suggest that premature relaxation of NPIs following vaccine introduction may compromise epidemic control.

Keywords
SARS-CoV-2 transmission dynamics
NPIs
COVID-19 vaccination
Bayesian analysis
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Information
  • Publisher :The Korean Society for Microbiology and The Korean Society of Virology
  • Publisher(Ko) :대한미생물학회‧대한바이러스학회
  • Journal Title :JOURNAL OF BACTERIOLOGY AND VIROLOGY
  • Volume : 56
  • No :1
  • Pages :58-72
  • Received Date : 2026-02-24
  • Revised Date : 2026-03-31
  • Accepted Date : 2026-03-31
  • DOI :https://doi.org/10.4167/jbv.2026.56.1.058
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