Abstract
Background: BCG have heterogeneous immunity to certain pathogens other than Mycobacterium tuberculosis effect. At early times during COVID-19 pandemic heterogeneous immunity towards (SARS-CoV-2), was hypothesized and statistical correlation between of BCG vaccination practices and COVID-19 mortality variances among countries was statistically proved. These studies was criticized because of low evidence of such studies and possible confounding factors. For that reason this study was designed to look for impact of duration of cessation of BCG programs on Covid-19 mortality looking for the hypotheses by different design and looking forward to support previous studies.

Methods: Total number of studied group is 14 countries which has stopped BCG vaccination programs. Through applying stem-leaf plot for exploring data screening behavior concerning Covid-19 Mortality for obsolescence duration of cessation of mass BCG vaccination programs, as well as (nonlinear regression of compound model) for predicted shape behavior for that group.

Results: Slope value shows highly significant effectiveness of obsolescence of cessation of mass BCG vaccination programs on Covid -19 mortality at P-value<0.000. Obsolescence of duration of cessation of mass BCG vaccination programs has strongly negatively associated with Covid-19 mortality in countries which stopped BCG vaccination programs.

Conclusion: The longer the cessation duration of BCG programs, the higher the Covid-19 mortality is, and vice versa.

Key words: Covid-19 Mortality, BCG Vaccination, Obsolescence of BCG Cessation.