COVID-19 excess mortality measured by the Global Health Security Index

By Neha MathurReviewed by Benedette Cuffari, M.Sc.Jul 13 2023

In a recent study published in BMJ Global Health, researchers compare coronavirus disease 2019 (COVID-19) excess mortality rates across 183 countries.

Study: Evaluation of the Global Health Security Index as a predictor of COVID-19 excess mortality standardized for under-reporting and age structure. Image Credit: ETAJOE / Shutterstock.com

Background

COVID-19, an infectious viral disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), quickly became the leading cause of death throughout the world after the pandemic began in March 2020.

Despite most countries implementing various measures to reduce the transmission of SARS-CoV-2, many of these policies were disjointed globally. Thus, it is crucial to examine country-level metrics of pandemic preparedness to ensure that nations throughout the world can implement effective responses in the future.

In addition to response capabilities, previous studies have also shown that many countries throughout the world were disproportionately affected by COVID-19 due to the unique age structure of their population.

For examples, countries with a higher proportion of elderly were more vulnerable to severe COVID-19. Likewise, each country's surveillance efforts determined their underlying risk for severe COVID-19.  

About the study

In the present study, researchers explore country-level associations between pandemic preparedness measures and age-standardized COVID-19 excess mortality across 183 countries. 

Comparative mortality ratios (CMRs) were calculated during the COVID-19 pandemic to account for country-level surveillance capacities and age structure variations. 

CMRs are a widely used form of indirect age standardization in epidemiological studies. These values utilize an age structure of mortality from a reference country which, in this case, was the United States, to compare mortality across countries, for comparisons of COVID-19 outcomes.

Mortality data from the Institute for Health Metrics and Evaluation’s (IHMEs) was used to model estimates for COVID-19 excess mortalities between January 1, 2020, and December 31, 2021. The demography of COVID-19 deaths database was used to extract age-specific COVID-19 mortality data to facilitate CMR computation.

Direct age standardization requires extensive age-stratified data on COVID-19 mortality, which is currently unavailable for most countries. For the current study, calculated age-stratified aggregate mortality rates for the U.S. and population sizes from the United Nations (UN) were used to determine age ranges.

Country-specific CMRs were also determined, in which a CMR greater than and less than one represented an increase and decrease in mortality relative to the reference country, respectively.

National preparedness efforts were assessed using the Global Health Security (GHS) index. This index has six categories of preparedness, 37 indicators, and a subset of sub-indicators that help quantify a country’s potential to prevent an infectious disease outbreak. Data on the GHS Index is publicly available for 195 countries, which the researchers used to identify a priori for analyses.

Pearson r correlations and multiple linear regression analyses were used to evaluate the relationship between GHS measures and COVID-19 CMRs. Additionally, bivariate regression models were used to assess each relationship independently of the other GHS indicators.

Confidence intervals (CIs) with robust standard errors were calculated and adjusted to account for testing multiple hypotheses using a Bonferroni correction. The coefficients and corresponding CIs represented CMR variations associated with five-point GHS index measure differences. A series of sensitivity analyses were also performed to determine the robustness of these results.

Study findings

There remains a shortage of comparable data from countries examining COVID-19 outcomes. Thus, detailed age-specific COVID-19 mortality rates are only available for 22 countries. Likewise, data on COVID-19 deaths are under-reported due to global variations in vital statistics performance. 

The GHS index was used as a predictor of COVID-19 excess deaths. After adjusting for higher GHS Index scores associated with lower CMRs for excess COVID-19 mortality, the implementation of efforts to prepare for and respond to pandemics before they occur could effectively reduce mortality during similar global health emergencies. 

Three GHS categories of prevention, detection, and response lowered excess COVID-19 deaths. For example, prevention approaches reduced excess COVID-19 deaths by reducing other infectious disease outbreaks. Furthermore, immunization capacities likely minimized the number of vaccine-preventable deaths and provided an infrastructure for successful vaccination programs.

Detection capacities related to laboratories engaged in case-based investigations lowered excess COVID-19 deaths. Likewise, emergency preparedness and responses, such as non-pharmacological interventions (NPIs), decreased excess COVID-19 deaths. 

Cross-border agreements were also found to be beneficial during a pandemic. One example includes countries in the European Union, which opened their borders to healthcare workers and those seeking medical care to share the pandemic burden.

The risk environment, a GHS index category, had the most consistent relationship with excess COVID-19 mortality. Despite ranking highest in the GHS Index of 57 high-income countries, the U.S. had the 30th largest risk environment score.

The study analyses also provided evidence that social and government support is crucial to respond to a health crisis. Thus, future studies should explore the role of other country-level capacities that are unrelated to excess COVID-19 deaths, including healthcare and intervention planning. 

The associations between pandemic preparedness capacities and excess mortality reduced to zero when using the WHO and The Economist data. WHO, the Economist, and Institute for Health Metrics and Evaluation (IHME) use different sets of covariates; thus, in countries with GHS scores less than 40, such as various African nations, COVID-19 deaths were undercounted by a factor of 10.

Conclusions

The GHS index is an inventory of resources and plans available within each nation to address a health crisis. The current analysis demonstrated that having greater health security capacities, as measured by the GHS Index, reduces excess COVID-19 mortality. Thus, investments in health systems could modulate pandemic outcomes. 

All countries require a well-established response infrastructure to address a health crisis, as well as an easily accessible, equitable, and competitive healthcare system for outbreak detection. In the future, building, maintaining, and measuring health security capacities could effectively mitigate the impacts of infectious disease threats.