COVID-19 immunological consequences: immunological significance of viro-allergy-hygiene hypothesis.

INTRODUCTION

Coronavirus disease 2019 (COVID-19) pandemic is assumed to begin in China with a group of severe pneumonia cases. Scientist are yet to fully understand effect and long time implication of this pandemic. This study aim at assessing infection (CF1) and mortality (CF2) indices across 154 countries to clarify these disparities and explore immuno-ecological explanations.

AREAS COVERED: One hundred and fifty four national data from WHO were normalized against the United States (CF1 = 1.0; CF2 = 1.0). Country-specific indices were calculated and grouped by WHO region. Regional means and standard deviations were generated, and comparative figures were produced to illustrate epidemiological patterns.

EXPERT OPINION: Europe (mean CF1 = 0.688; CF2 = 0.727) and the Americas (CF1 = 0.445; CF2 = 0.705) showed the highest combined burdens. Certain countries, including Peru, Hungary, and Bosnia, recorded disproportionately elevated mortality indices (CF2 > 1.5). Africa consistently showed near-baseline values (CF1 = 0.058; CF2 = 0.073), while the Western Pacific (CF1 = 0.175; CF2 = 0.094) and South-East Asia (CF1 = 0.274; CF2 = 0.175) demonstrated low mortality. The viro-allergy-hygiene hypothesis offers a plausible explanation, suggesting that repeated microbial exposures, endemic infections, and trained immunity recalibrate host responses and mitigate severe outcomes.