Document Type : Original Article


1 Student Research Committee, Department of Epidemiology, School of Public Health and Safety, Shahid Beheshti University of Medical Sciences, Tehran, Iran

2 HIV/AIDS Research Center, Shiraz University of Medical Sciences, Shiraz, Iran

3 Department of Epidemiology, School of Public Health & Safety, Shahid Beheshti University of Medical Sciences (SBMU), Tehran, Iran


Background: In 2020, shortly after recognizing the COVID-19 virus in China on March 11, the World Health Organization (WHO) declared the Covid-19 outbreak a pandemic. It is estimated that COVID-19 is responsible for millions of morbidities and deaths globally, causing devastating health, social and economic crises. This ecologic study aimed to define the correlation between a few key elements of a national health system (i.e., quality of health care services, rate of provided COVID-19 diagnostic tests, and coverage of flu vaccine in the preceding years of the COVID-19 pandemic) and the fatality rate of COVID-19 in countries that were affected by the Covid-19 epidemic in the early phase of the pandemic.
Methods: In this ecological study, data regarding the total population, number of active cases, total cases, mortality, and time to peak of the COVID-19 epidemic for the countries with defined criteria and the required data available were collected from the Worldmeter database. Thehealth system quality of the selected countries was obtained using a report by WHO (Measuring Overall Health System Performance for 191 Countries). The Flu vaccine coverage of the selected populations was ordered and ranked using graphs provided by a joint VENICE–ECDC–WHO survey. The analysis was done by fitting meta-regression using rates and confidence intervals. A forest graph was used to show the summary of the results. R version 6.3 (package meta) was used to do the analysis.
Results: The average Case fatality rate (CFR) of the 26 selected countries was 115 per 1000 for COVID-19. Testing for heterogeneity suggested that CFR was highly heterogeneous among the countries. The regression analysis results suggested that CFR for COVID-19 was inversely related to the rate of COVID-19 diagnostic tests and was directly related to the rate of flu vaccine coverage).
Conclusion: The direct correlation between flu vaccine coverage and CFR of COVID-19 may suggest a positive effect of the natural circulation of flu infection on the effectiveness of the individuals’ immune response. Also, the natural flu infection may protect those who could not tolerate the respiratory complications of COVID-19 infection. The results may help NHSs to cope better with future pandemics. In addition, to provide a faster and more effective response to any future infectious pandemic, better access to diagnosis tests seems to be an effective approach in reducing morbidity and mortality.


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