Interaction between malarial transmission and BCG vaccination with COVID-19 incidence in the world map: A changing landscape human immune system? (Preprint)
<title>BACKGROUND</title> <p>COVID-19 (Corona virus Disease-2019) is a new public health emergency and is a pandemic currently. Incidence and mortality of COVID-19 vary in different geographical areas.</p> <title>OBJECTIVE</title> <p>In this study we aimed to analyse the relationship between malaria transmission and BCG vaccination with COVID-19 incidence in the world map.</p> <title>METHODS</title> <p>We collected malaria cases data (World Health Organisation (WHO), 2018), worldwide COVID-19 cases and mortality data (European Centre for Disease Prevention and Control) and data on BCG vaccination. COVID-19 incidence and mortality was compared.</p> <title>RESULTS</title> <p>Data on 5316978938 persons from 166 countries were analysed. Malaria incidence rate was negatively correlated with COVID-19 incidence rate (correlation coefficient = -0.513, p<0.001). Malaria free countries had significantly higher number of COVID-19 cases compared to malaria endemic countries. In Europe and Americas, countries, which have higher BCG vaccination coverage, had significantly less mortality per thousand population compared to those with low BCG coverage (median 0.0002 (0-0.0005) vs 0.0029 (0.0002-0.0177), p=0.017). The case fatality ratio of COVID-19 was related nonlinearly to the malaria incidence.</p> <title>CONCLUSIONS</title> <p>The results suggest the changing human immune system as we progress to eliminate parasitic diseases with time. Chloroquine exposure in malaria endemic zones might have a protective effect.</p>
