When evaluating vaccine efficacy, the conventional measures include a reduction of risk of hospitalization and death. The number of patients dying with or without vaccination is often in the public spotlight. However, when evaluating public health interventions or the burden of disease, it is more illustrative to use mortality metrics taking into account also prematurity of the deaths, such as years of life lost (YLL) or years of life saved (YLS) thanks to the vaccination.
Researchers from the Faculty of Science at Charles University used this approach to evaluate the difference in YLL and YLS between COVID-19 victims with or without completed vaccination in the autumn pandemic wave (2021, October–December) in Czechia. For the analysis, individual data about all COVID-19 deaths in the country was used. While 40.6% of the deaths are in cohorts with completed vaccination, this corresponds to 35.1% of years of life lost. The role of vaccination is expressed using YLS and hypothetical numbers of deaths. The registered number of deaths is approximately 3.5 times lower than it would be expected without vaccination. The results illustrate that vaccination is more effective in saving lives than suggested by simplistic comparisons.
The COVID-19 pandemic emphasized the need for an interdisciplinary approach. The role of demography is irreplaceable in the case of evaluation of its consequences for the population and the effectiveness of applied measures above all. The study has proposed a method usable in this evaluation and contributes to the topic of vaccine effectiveness using demographic and mathematical methods. Metrics such as YLL should be considered when evaluating the impacts of various population-wide interventions. Assessing years of life lost is a good indicator of the effects of a pandemic, as it provides a much more relevant view than the crude mortality rate (numbers of deaths per population size) often used in practice. In this study, the measure of YLL was used not only for illustration of the outcome of the pandemics but above all for the evaluation of the effect of completed vaccination. It provides clear evidence of the benefits of COVID-19 vaccination and using the YLS illustrates the advantage of the population with complete vaccination as compared to the population without it.
The result illustrates that vaccination is even more effective in saving lives than suggested by straightforward and often simplified comparisons. “Moreover, in the case of Czechia, among the population with completed vaccination, almost 15 thousand COVID-19-related deaths were potentially avoided. Vaccination helped to reduce the YLL among the fully vaccinated by around 88% during the studied period and the registered number of deaths is approximately 3.5 lower than it would be expected without vaccination,” concluded researchers Dr. Hulíková Tesárková & Dr. Dzúrová. The study demonstrates that COVID-19 vaccination saves lives and saves years of potential future lives.
The text is based on the research article:
Hulíková Tesárková, K., Dzúrová, D. COVID-19: years of life lost (YLL) and saved (YLS) as an expression of the role of vaccination. Sci Rep 12, 18129 (2022). https://doi.org/10.1038/s41598-022-23023-0
