Back ground : Latent TB disease reflect a state of persistent immune response to stimulation by Mycobacterium tuberculois . TB infection lead to latent TB disease in 90-95 % while 5-10 % of individuals develop active TB disease when compared to BCG , BCG is 60% effective against the development of active TB. Studies done to test association of BCG with covid-19 morbidity and mortality and it was thought that BCG have preventive effects due to presumed non specific anti viral effects in this study we test association between prevalent of TB which reflects about 90-95 % of corresponding latent TB infection with covid 19 mortality. Materials and methods : countries divided into 5 groups according to BCG following status : No vaccination at all no previous BCG group , no current but had BCG in past (one or more), 1 current BCG with previous booster (s) , just 1 BCG now no previous booster (s) and more than 1 BCG setting now. covid -19 deaths taken as it is on these are tested against TB prevalence 2018. Results: Slop values have significant influences between TB prevalence and covid -19 deaths among all tested groups and are reversed in just 1 BCG now no previous booster (s) groupP<0.01 coefficient (0.30751) ,1 current BCG with previous booster (s) P<0.01 coefficient (0.63662) , and more than 1 BCG setting now group P<0.05 with coefficient of (0.61580). While no vaccination at all no previous BCG group shows Compound model linear regression P<0.05 coefficient ( 97.45%)and No current but had BCG in past (one or more) group shows Cubic model P<0.01, coefficient (66.098%)The overall slope value is highly significant and reverse influence at P<0.01, as well as highly significant relationship coefficient (0.36749). The linear regression model obtained in logarithmic mode for all tested sample and being inverse in countries with more than 1 BCG setting at this time and countries with 1 current BCG with previous booster (s) furthermore linear regression model is logarithmic in countries with just 1 BCG now and no previous booster (s) . Introduction:About one-quarter of the world's population may be infected with latent tuberculosis 1 which is defined as a state of persistent immune response to stimulation by Mycobacterium tuberculosis antigens with no evidence of clinically manifest active TB 2 . It is estimated that the lifetime risk of an individual with LTBI for progression to active TB is 5-10% 3 , furthermore more than 90% of people infected with M. tuberculosis for more than two years never develop tuberculosis even if their immune system is severely suppressed 4 ,while BCG is highly efficacious at preventing meningeal and miliary TB, but is at best 60% effective against the development of pulmonary TB in adults and wanes with age. 5 It is hypothesized that beneficial heterologous non-specific effects and innate immune memory training through epigenetic reprogramming. 5 , 6 Furthermore secretion of pro-inflammatory cytokines, specifically IL-1B play a vital role in antiviral immunity this is believed to be increased b...

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Background: Regarding SARS-CoV-2 it is well known that a substantial percentage of adult population cannot get infected if exposed to this novel coronavirus. Several studies give primary indication of the possible role of preexisting immunity whether cross immunity or not. Possible role of latent TB and BCG and malaria have been already suggested to create innate cross heterogeneous immunity. We look for influence of these factors on Covid-19 mortality in malarious countries. Material and methods:80 malarious countries are enrolled in this study. Hierarchical multiple regression type of analyses is used for data analyses. TB prevalence/ 100,000 population standardized to BCG coverage rates is taken as direct factor in the test. Malaria incidence /1000 population is considered as intermediate factor and the outcome is COVID-19 mortality/ 1 million (M) population. Results: TB prevalence is associated with reduced COVID-19 mortality and malaria have an additional effect in reducing COVID-19 mortality. The results show with robust statistical support that TB prevalence was also associated with reduced COVID-19 mortality with additional effect that is also observed in TB and BCG coverage rate. Conclusions: Malaria and standardized TB prevalence are statistical significant factors predicting COVID-19 mortality in negative associations.

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Background: Emergence of new multisystem inflammatory syndrome in children (MIS-C) is thought to be associated with COVID-19 pandemic. Covid-19 morbidity and mortality variances among countries have been suggested by previous works to be influenced by BCG and previous latent TB infection (which is reflected by TB prevalence) possibly through inducing heterogeneous immunity against SARS-CoV-2. Aim: To examine influence of BCG status and TB prevalence on variances among countries which report new multisystem inflammatory syndrome in children (MIS-C). Methods: We choose all countries which report MIS-C till 23/6/2020, number of cases for each 10 million inhabitants was examined among 3 categories of countries classified according to BCG program status. TB prevalence, MIS-C no. / 10 million (M) population and Covid- 19 deaths/M are taken as markers. Receiver operation characteristic - (ROC) curve, with some relative indicators such as (sensitivity and specificity rates), estimation area of trade - off between sensitivity and specificity, and cutoff points are used with different studied markers for discriminating different three pairs of countries (which have different BCG practices). Results: MIS-C No/10 M inhabitants in countries never gave BCG vaccination versus (vs) countries currently give vaccine shows area under ROC- curve equal to 0.000 with a symbiotic significant of 0.034 and (95% CI interval of 0.000-0.000) also MIS-C No/10 M inhabitants in countries not currently give BCG vaccination ( with previous mass vaccination programs) vs countries currently give mass vaccination shows area under ROC- curve equal to 0.094 with a symbiotic significant of 0.027and ( 95% CI interval of 0.000 -0.280). Important not significant finding MIS-C No/10 M inhabitants in countries never gave BCG vaccination vs countries not currently give vaccine shows area under ROC- curve equal to 0.583 with a symbiotic significant of 0.683 and (95% CI interval of 0.074-0.759). COVID-19 deaths / M inhabitants in countries never gave BCG vaccination vs countries currently give vaccine show area under ROC- curve equal to 0.083 with a symbiotic informative and reportable value of 0.077 and (95% CI interval of 0.000-0.309 also COVID-19 deaths/ M inhabitants in countries not currently give BCG vaccination vs countries currently giving vaccine show area under ROC- curve equal to 0.188 with a symbiotic informative reportable value of 0.089 and ( 95% CI interval of 0.000-0.452). Important finding is the not significant association of COVID-19 deaths /M inhabitants with countries never gave BCG vaccination vs countries not currently giving vaccine area under ROC- curve equal to 0.417 with a symbiotic significant of 0.683 and (95% CI interval of 0.078 - 0.755). Regarding TB prevalence marker or discriminator the areas under curve were informative and reportable and too generating with the leftover markers in all 3 pairs of countries signifying inverse relations with covide-19 mortality and MIS-C no. Conclusions: BCG vaccinations and high TB prevalence are found to be related to decrease MIS-C no. and COVID-19 deaths this might explain variances among countries worldwide. Further studies to confirm this relation and to confirm possible similar relations in Kawasaki disease(KD) or KD like illnesses in previous epidemics is recommended. Review of TB programs and consolidation of BCG programs might be considered urgently.