Covid 19 Morbidity and Case Fatality Rate: An Analysis of PossibleConfounding Factors

Abstract

Introduction: When the first report appeared of a protective effect of universal BCG vaccination on COVID- 19 morbidity and case fatality rates, as well as referring to previous papers on the nonspecific protective effects of BCG, our interest was raised, because Mozambique was in an unusual position in relation to BCG vaccination. Based on our knowledge of the history of global public health, we constructed a table with the number of cases of COVID-19 per 100,000 inhabitants and the case fatality rate of the countries that had carried out universal BCG vaccination for a long period (India, Japan and the ex-USSR countries), compared to countries without a universal BCG vaccination programme. We found that countries that had carried out universal BCG vaccination for a long period had much lower case/population ratios and case fatality rates than those without a universal BCG vaccination programme. This exercise was repeated three times, during the month of April, with consistent results. These results made us take the decision to undertake a study of possible confounding factors.

Mozambique became independent in June 1975, and immediately after carried out a mass vaccination campaign with the six antigens of the recently created EPI. Smallpox vaccine was added, in order to consolidate smallpox eradication. WHO, at that time, was against vaccination campaigns, but an exceptional agreement was obtained. The campaign took place from the north to the south of the country, from February 1976 to January 1978. Every province started a routine EPI programme as soon as the campaign finished. In the campaign, all children 15 years old or younger received BCG vaccine. The coverage rate in the campaign was 97%, with 99% in the capital city of Maputo. Subsequently, the coverage rate of BCG vaccination at birth in the EPI has been always remarkably high in urban areas. In rural areas, coverage has been irregular, but has been at least 80% in the past 25 years. Therefore, most of the urban population aged 58 or less has received BCG, and so has an important part of the rural population. Such a high coverage of BCG is exceedingly rare in the world.

We have analysed the factors that may influence the development of COVID-19 epidemics and concluded that, apart from the virulence of the virus (that we do not have enough data to study), other factors are important, namely, the immune state of the population, the demographic profile and socioeconomic characteristics of the population, ecological and meteorological factors and, finally, the prevention measures taken and the degree of their implementation. Taking into consideration that most countries, with more or less firmness, have followed the WHO recommendations, on measures for prevention and control of COVID- 19, we decided not to analyse these measures. Our study therefore emphasised the other factors.

Methods: Our analysis focused on 82 countries, with more than 10 million inhabitants, which together correspond to 72.2% of the world population, distributed in three groups: northern hemisphere (above latitude 23º N), intertropical zone (between 23º latitude N and 23º latitude S) and southern hemisphere (below 23º latitude S). We have studied the relationship of BCG vaccination policies on the number of cases per 100.000 inhabitants and the case fatality rate, in the first 60 days and the first 90 days of the COVID-19 epidemics, in each country. We are performing bilateral and multilateral statistical analysis of variables related to climate (temperature, humidity and ultra-violet radiation), HIV prevalence and ART coverage, malaria (incidence and case fatality rate), tobacco and Vitamin D.

Results: The results are being analysed and will be published later.

Conclusions and Preliminary Recommendations: There is evidence of the non-specific protective effects of BCG, as well as negative statistical correlations on the malaria / COVID-19 ratio. However, there are still no conclusive proofs. There is scientific evidence on the beneficial effects of solar radiation (ultraviolet radiation) mediated by Vitamin D, which calms the cytokine storm caused by COVID-19.

The population is recommended to regularly expose themselves to the sun, using the slogan: “Take the sun staying at home”. We also recommend the systematic administration of Vitamin D to all symptomatic cases of COVID-19 and that doctors be instructed on the appropriate doses of Vitamin D.

Declaration of No Conflict Of Interest: The authors have declared that they have not received any financing to perform this research and that they have no competing financial interests or personal relationships that could represent conflict of interest.