SARS-CoV-2 Genetic Variability and Non-Specific Immunity Associated with the Use of Different BCG Strains-A Molecular and Clinical Approach.

Jakub Kulus,Hanna Piotrowska-Kempisty,Bartosz Kempisty,Paul Mozdziak,Jarosław Sobolewski,Magdalena Kulus,Katarzyna Stefańska

doi:10.3390/vaccines9060639

Jakub Kulus, Hanna Piotrowska-Kempisty + Show 5 more

Open Access

https://doi.org/10.3390/vaccines9060639

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Abstract

The effect of BCG vaccination against tuberculosis on the reduction in COVID-19 infection is related to the effect of the BCG vaccine on the immunomodulation of non-specific immunity. In the early stages of the pandemic, countries with universal BCG vaccination programs registered a low number of new cases of COVID-19, with the situation now reversed, as exemplified by India. The high genetic variability of SARS-CoV-2, a known characteristic of RNA viruses, causing the occurrence of SARS-CoV-2 variants may have led to the virus adapting to overcome the initial immune protection. The strains from the United Kingdom (B1.1.7), Brazil (B1.1.28 and B1.1.33), South Africa (B.1.351), and India (B.1.617) are characterized by a greater ability to spread in the environment, in comparison with the original infectious agent of SARS-CoV-2. It should be remembered that the large variation in the genetic makeup of SARS-CoV-2 may result in future changes in its pathogenicity, immunogenicity and antigenicity, and therefore it is necessary to carefully study the mutations occurring within the virus to determine whether the current vaccines will remain effective. However, most studies show that monoclonal antibodies produced after vaccination against COVID-19 are effective against the newly developed variants.

Highlights

The current coronavirus disease (COVID-19) pandemic has affected the whole world since 2020
The high genetic variability described within SARS-CoV-2, manifested by the description of new viral variants, should be carefully analyzed
Based on the data presented here, it can be seen that in the early stages of the pandemic, Bacillus Calmette–Guérin (BCG) vaccination used on a large scale in selected countries resulted in lower mortality in those countries due to COVID-19

Summary

Introduction

The current coronavirus disease (COVID-19) pandemic has affected the whole world since 2020. The study by Escobar et al [2], consistent with other epidemiological studies [3,4], suggests an association between a lower number of cases and diminished mortality from COVID-19 with the presence of national mandatory BCG vaccination programs. The reasons may include delays in COVID-19 death reporting, as well as the misattribution of COVID-19 deaths to other illnesses either resembling COVID (pneumonia) or reflecting its complications (myocarditis, coagulopathy) [9] These findings reveal that estimating the COVID-19 death toll considering excess allcause mortality may be more reliable than being based only on reported deaths, especially in countries with an insufficient testing capacity [8]. Previous studies [4,10] have shown that countries adopting BCG-Japan or a mixture of different BCG vaccine strains reported a lower number of confirmed and fatal COVID-19 cases. Even if BCG vaccination does contribute to reducing COVID-19 mortality, it is definitely not the only factor, as can be illustrated by Australia and Finland’s cases, which report low COVID-19 deaths despite refusing mandatory BCG vaccination [4]

The Specificity of SARS-CoV-2—Molecular Characteristics

Genetic Variability of SARS-CoV-2

The Characteristic of BCG Strains

The BCG Vaccination—Current Strategies and WHO Recommendations

Conclusions