Summary of findings
The present study estimated total, sex-specific and age-specific excess all-cause mortality in 24 countries during the years 2020 and 2021. The majority of investigated countries showed significant excess mortality during at least 1 week of 2020 and 1 week of 2021, with varying duration. Australia, Denmark, Mauritius and Ukraine did not display excess mortality for any week during both years 2020 and 2021, while Norway did not display excess mortality during 2020, and France and Italy during 2021. Moreover, excess mortality was higher for people aged 65+ years and 70+ years than in younger age groups (<65 and <70) in most countries.
Excess of cumulative ASMRs was reported in all countries analysed in 2020 and/or 2021, except for Australia and Mauritius. Denmark showed no statistically significant differences in all-cause mortality rate in 2020 and Mauritius demonstrated a statistically significant decrease in yearly all-cause mortality rate during both years. The highest estimated excess mortality rate for 2020 was 273 deaths per 100 000 population in Peru, while the highest estimated excess mortality rate for 2021 was 338.7 deaths per 100 000 population in Kazakhstan. These findings are in accordance with those reported elsewhere, regardless of the use of different methodologies and data sources.22 24 38 39 More specifically, Nepomuceno et al, using a combination of different methodologies, demonstrated that Italy, the USA, Slovenia and countries of the UK were the most heavily affected in terms of ASMRs.40 Additionally, Karlinsky and Kobak estimated excess deaths by using data from the World Mortality Dataset until the end of 2020 or the first half of 2021, and showed that Peru, Brazil, the USA, Italy and countries of the UK were the most affected.41 COVID-19 Excess Mortality Collaborators (2022) have also identified Italy, Greece, Norway, Spain, Sweden and the USA as having a high excess of all-cause deaths.22
The cumulative excess for all-cause mortality for the total population in 2020 was higher than in 2021 in Austria, Belgium, England and Wales, France, Italy, Mauritius, Slovenia, and Spain. This may be due to the COVID-19 vaccination programmes that have been shown to reduce at least COVID-19-related mortality,3 42 or due to the time of different waves as in the case of Belgium where a second wave arrived in late 2020 rather than early 2021.43 The same scenario applies to both female and male populations, with the exception of Slovenia where for females the cumulative excess for all-cause mortality was higher in 2021 than in 2020. These results align with other published results. The Our World in Data also shows that in France, Belgium, Italy and Spain, excess mortality in 2020 was higher than in 2021.44
In the yearly cumulative comparison, increases or decreases in all-cause mortality were similar between sexes in both years except for Mauritius (statistically significant decrease only in females in 2020), Norway (statistically significant increase only in males in 2020), Ukraine (statistically significant increase only in males in 2020) and Belgium (statistically significant increase only in males in 2021). Moreover, males were more affected than females in terms of cumulative excess ASMR, with the exception of Australia and Mauritius in 2020, and Australia, Denmark, Mauritius and Ukraine in 2021. Many studies have previously reported the male predominance in excess mortality in most countries.15 24 45–47 This may be due to a number of factors, such as occupation and lifestyle factors, or differences in comorbidities between males and females that may rise the possibility of SARS-CoV-2 exposure among males than females.24
The observed pattern of weekly excess mortality in the countries included in the current study demonstrates that some countries experienced substantial excess mortality during the first half of the year but not later, for both 2020 and 2021 (Kazakhstan, Peru, Spain in 2020, Brazil in 2021), while other countries did so during the second half of the year but not earlier (Austria, Georgia, Greece, Israel in 2020 and 2021). Similar peaks in excess mortality for the participating countries were reported elsewhere.22 24 41 44
Of the country-level sociodemographic variables investigated, hypertension, diabetes and obesity prevalence, as well as Gini index were positively associated with increased excess mortality, whereas HDI, hospital beds per 1000 population and HAQ were inversely associated with excess mortality as also shown elsewhere.22 48–54 Interestingly, completeness of vital registration and excess mortality were significantly positively associated when the multivariable model was restricted to countries with higher than 90% of completeness. Below that completeness level, multiple factors unique to under resourced health system settings are likely to influence the death rate, and deaths recording, and as a result the observed relationship with excess deaths is likely underestimated and biased. Therefore, interpretation of results from countries with less than 90% of completeness in their vital registrations should be treated with caution, as the observed mortality rates may underestimate the true excess mortality.
In the multilevel models investigating pandemic-related variables, the random effect of country explains a substantial proportion of the variability in the outcome, highlighting that different countries had a different experience with respect to the determinants of excess mortality. It is also important to highlight that in these models, the coefficients returned are an average of the experience of the included countries. Weekly reported incidence of COVID-19 significantly increased excess mortality during both years. Seroprevalence was also shown to be associated with excess mortality elsewhere.22 During 2020, contrary to expectations,16 the stringency of control measures was positively associated with excess mortality, whereas, during 2021, those countries that retained strict control measures experienced less excess mortality. In the time-varying models that investigated the effects of stringency on excess mortality, across 2020–2021, in each country independently, substantial fluctuations are evident in the observed coefficients suggesting that it might not be the overall stringency of measures, but specific policies that had a greater benefit in mitigating excess mortality in each country. Nevertheless, for most countries, despite the fluctuations, the coefficients were in the negative range for most of the duration of the 2 years indicating an overall protective effect of the stringency of control measures.
In the multilevel model for 2021, no significant association was observed between vaccination rates and excess mortality, despite a clear and significant trend between maximum achieved vaccination coverage and cumulative excess mortality, across countries, in 2021 (online supplemental figure S27). This non-significant association is likely attributed to the different experience of each country in terms of the prioritising older and vulnerable populations in vaccine distribution and to the variability of the development level of participating countries since high-income countries tended to have greater vaccine access, and managed to cover larger proportions of their older and at-risk populations. Conversely, lower-income and middle-income countries, such as Georgia and Ukraine, experienced delays in achieving sufficient vaccination coverage compared with high-income countries. Consequently, substantial benefits may not have been reflected during 2021. Similarly, as seen in online supplemental figures S6–S27, for many countries, sharp increases in vaccine coverage coincided with the increasing prevalence of the more virulent Delta variant (between July and November 2021), something that could be masking beneficial effects of vaccination. Vaccinations did benefit excess mortality through interaction with weekly incidence of reported COVID-19 cases; in countries and weeks with higher than average vaccination rates, increases in incidence of COVID-19 did not lead to as high excess mortality as compared with countries and weeks with average vaccination rates.
Despite the variable experience of countries, the time-varying models for vaccination display some common features between countries. Several countries (Austria, Belgium, Denmark, England and Wales, France, Israel, Northern Ireland, Norway, and Sweden) had negative coefficients for the association between vaccination coverage and excess mortality, during the first weeks of vaccine introduction, suggesting that the first wave of vaccinations that, in most countries prioritised older and vulnerable portions of the population, managed to mitigate excess mortality. For most of these countries, the coefficients of the association then increased to zero or even positive numbers. In fact, Australia, Austria, Belgium, Denmark, England and Wales, Norway, Poland, Slovenia, and Northern Ireland experienced positive coefficients during the second half of 2021, which could be explained by waning effectiveness of the first vaccinations, as well as by the rise in prevalence of the Delta variant. On the other hand, Brazil, Cyprus, Georgia, Greece and Italy all started with positive coefficients that declined as vaccination coverage increased. The reasons for the different experiences in these latter countries remain to be investigated.