Epidemiological Differences of COVID-19 Over the World

Abstract

Background Coronavirus disease 2019 (COVID-19), originally, from Wuhan, China, has now spread to most countries across the globe and devastated global healthcare systems. The impact of this disease has, however, shown baffling variations in prevalence in different regions of the world. The aim of this short review is to identify differential national COVID-19 prevalence of COVID-19, as well as to suggest these epidemiological differences. Methods A review of studies was conducted using PubMed and Google Scholar search engines. Search tactics were centered on COVID-19 ("COVID-19" AND "coronavirus") and BCG vaccination ("BCG vaccination" OR "Bacillus Calmette-Guérin" OR "vaccine") Results It is found that national prevalence differences may be linked with BCG childhood immunization history. A statistically insignificant difference was observed in COVID-19 prevalence when comparing countries with a BGC policy and countries without it (P> 0.05). This inconclusivity suggests the influence of confounders in this study. Conclusions National differences in COVID-19 cases can be attributable to immunologic regulations, such as BCG vaccination protocols. Caution should be taken in establishing a correlation between COVID-19 prevalence and BCG vaccination, partly due to the weak quality of statistical data on COVID-19 related to poor testing rates in countries with BCG vaccination policy. Nonetheless, the analysis of the epidemiological aspects of COVID-19 will shed light on future efforts towards effective control and prevention.

Production of SARS-CoV-2 Antibodies and Emergence of the Clinical Symptoms of COVID-19

“…SARS-CoV-2 continues to affect every region of the world, but some countries are experiencing high rates of infection, while others appear to have mostly controlled the virus. 10 It's well documented that many patients may have been contaminated person to person by asymptomatic patients. Therefore, asymptomatic patients can be considered as a source of infection and they can spread the virus, and consequently, large-scale transmission from asymptomatic patients is suspected.…”

BCG Vaccination: A potential tool against COVID-19 and COVID-19-like Black Swan incidents

“…Escobar et al performed an epidemiological study, after eliminating the potential confounding factors such as the COVID-19 epidemic stages, geographical distribution, population density, and age structure, they found a 10% increase in the BCG index resulted in a 10.4% decrease in COVID-19 deaths [88] . Interestingly, a large number of subsequent ecological studies have found a similar phenomenon that BCG vaccination rates and years of implementation of the BCG vaccination policy are significantly negatively correlated with COVID-19 morbidity and mortality [14] , [89] , [90] , [91] , [92] , [93] , [94] , [95] , [96] , [97] , [98] , [99] , [100] , [101] , [102] , [103] , [104] , [105] , [106] , [107] , [108] , [109] , [110] , [111] , [112] , [113] .…”

The Natural Effect of BCG Vaccination on COVID-19: The Debate Continues

“…In the early months of the COVID-19 pandemic, findings from the ecological and analytical studies indicated that countries with low BCG coverage had significantly higher rates of COVID-19 morbidity and mortality than countries with high BCG coverage . On the contrary, other ecological and analytical studies found that BCG vaccination could not provide adequate protection against COVID-19 infection (41)(42)(43)(44)(45)(46)(47)(48)(49)(50). The results of these ecological and analytical studies were contradictory, and the heterogeneity of these findings may originate from some confounding factors, such as population density, ethnicity, age structure, income, healthcare access and quality index, COVID-19 transmission progression, COVID-19 testing rate, nonpharmaceutical interventions, and geographical distribution (2, 5, 51-53).…”