There is a significant difference between COVID 19 associated mortality between different countries. Generally the number of deaths per million population are higher in the developed countries despite better health care efficiency, drinking water quality and expected healthy life span (HALE) at the time of birth. Developing and underdeveloped countries on the other hand have lower mortality even with higher rural and slum populations along with incidence of diarrhea because of lack of sanitation. We analyzed data from 122 countries out of which 80 were high or upper middle income and 42 were low or low middle income countries. There was statistically significant positive correlation between COVID 19 deaths /million population and water current score, health efficiency, and HALE. Statistically significant negative correlation was observed with % rural population and fraction of diarrhea because of inadequate sanitation for all ages. Moreover analysis of 51 countries showed that there is significant negative correlation between COVID 19 deaths /million population and proportion of total population living in slums. We propose that high microbial exposure particularly gram negative bacteria can possibly induce interferon type I which might have a protective effect against COVID 19 since the countries with less mortality also tend to have lack of sanitation and high incidence of attendant diseases. So, far none of the predictive models have taken into account immune status of populations engendered by environmental microbial exposure or microbiome. There might be a need to look at dynamics of COVID 19 pandemic using immune perspective. The approach can potentially inform better policies including interventions.
