COVID-19 Vaccination Efforts Prevented 20 Million Deaths Worldwide, Study Estimates

Global COVID-19 deaths averted through vaccination based on excess mortality
(A) Average number of daily COVID-19 deaths based on excess mortality estimates (gray vertical bars) in the first year of vaccination. The baseline estimate of daily COVID-19 deaths from the model fit to excess mortality is plotted with the solid black line and the counterfactual scenario without vaccines is plotted with a red line. The space between the red and black line indicates deaths averted due to vaccination, with the proportion of total deaths averted by direct protection conferred by vaccination in blue and indirect protection in green. (B) Average number of daily deaths prevented per day by 2022 World Bank income group.

Comments

• The first modeling study to quantify the impact of COVID-19 vaccines on a global scale estimates that 19.8 million of a potential 31.4 million deaths were averted in the first year after the vaccines were introduced (8 December 2020 - December 8, 2021).
   
• High- and upper-middle-income countries accounted for the highest number of deaths prevented (12.2 million/19.8 million), highlighting inequalities in vaccine access around the world.
   
• Another 599,300 deaths could have been avoided if the World Health Organization’s goal of vaccinating 40% of the population in all countries by the end of 2021 had been met.
   
• The study is based on data from 185 countries and territories and is the first to assess deaths averted directly and indirectly as a result of COVID-19 vaccination, using COVID-19 death records and total excess deaths from each country (or estimates in which official data were obtained).

COVID-19 vaccines reduced the potential number of global deaths during the pandemic by more than half in the year after they were implemented, according to estimates from a mathematical modeling study published today in The Lancet Infectious Diseases .

Dr Oliver Watson, lead author of the study, from Imperial College London, said: “Our findings offer the most comprehensive assessment to date of the remarkable global impact that vaccination has had on the COVID-19 pandemic. Of the nearly 20 million deaths estimated to have been averted in the first year after the introduction of vaccines, nearly 7.5 million deaths were averted in countries covered by the COVID-19 Vaccine Access Initiative ( COVAX). This initiative was created because from the beginning it was clear that global vaccine equity would be the only way out of the pandemic. Our findings show that millions of lives are likely to have been saved by making vaccines available to people everywhere, regardless of their wealth. However, more could have been done. “If the targets set by WHO had been met, we estimate that approximately 1 in 5 of the estimated lives lost due to COVID-19 in low-income countries could have been avoided.”

Since the first COVID-19 vaccine was administered outside of a clinical trial setting on December 8, 2020, nearly two-thirds of the world’s population has received at least one dose of a COVID-19 vaccine (66% ). The COVID-19 Vaccine Access (COVAX) initiative has facilitated access to affordable vaccines for lower-income countries to try to reduce inequalities, with an initial goal of giving two vaccine doses to 20% of the population in countries covered by the commitment by the end of 2021. The World Health Organization expanded this goal by establishing a global strategy to fully vaccinate 70% of the world’s population by mid-2022, with an interim goal of vaccinating 40% of the population of all countries by the end of 2021.

Despite the incredible speed of the vaccine rollout around the world, more than 3.5 million COVID-19 deaths have been reported since the first vaccine was administered in December 2020.

Several studies have tried to estimate the impact of vaccination on the course of the pandemic. These studies have focused on specific regions, such as individual countries, states, or cities. The latest study is the first to estimate the impact of COVID-19 vaccines on a global scale and the first to assess the number of deaths prevented both directly and indirectly.

Study co-author Mr Gregory Barnsley, from Imperial College London , said: "Quantifying the impact vaccination has had globally is challenging because access to vaccines varies between countries, as does our understanding of which variants of COVID-19 have been in circulation, with very limited genetic sequence data available for many countries. It is also not possible to directly measure how many deaths would have occurred without the vaccines. Mathematical modeling offers a useful tool to evaluate alternative scenarios, which we cannot observe directly in real life.”

To estimate the impact of global vaccination programs, the researchers used an established model of COVID-19 transmission using country-level data for officially recorded COVID-19 deaths that occurred between December 8, 2020 and December 8. December 2021. To account for underreporting of deaths in countries with weaker surveillance systems, they conducted a separate analysis based on the number of excess deaths recorded above those that would have been expected during the same period of time. When official data were not available, the team used estimates of excess mortality from all causes. These analyzes were compared to an alternative hypothetical scenario in which no vaccines were delivered.

The model took into account variation in vaccination rates between countries, as well as differences in vaccine effectiveness in each country based on the types of vaccine known to have been predominantly used in those areas. Notably, China was not included in the analysis due to its large population and very strict lockdown measures, which would have skewed the results.

The team found that, based on officially recorded COVID-19 deaths, approximately 18.1 million deaths would have occurred during the study period if vaccines had not been rolled out. Of these, the model estimates that vaccination has prevented 14.4 million deaths , representing a global reduction of 79% . These findings do not take into account the underreporting of COVID-19 deaths, which is common in low-income countries. The team did an additional analysis based on total excess deaths over the same time period to account for this. They found that COVID-19 vaccination prevented approximately 19.8 million deaths out of a total of 31.4 million potential deaths that would have occurred without vaccination, a 63% reduction.

More than three-quarters (79%, 15.5 million/19.8 million) of the deaths prevented were due to the direct protection against severe symptoms provided by vaccination, leading to lower mortality rates. The remaining 4.3 million avoided deaths were estimated to have been averted through indirect protection by reducing transmission of the virus in the population and reducing the burden on healthcare systems, thereby improving access to healthcare. for those most in need.

The impact of the vaccine changed over time and in different areas of the world as the pandemic progressed, the study found. In the first half of 2021, the highest number of deaths prevented by vaccination was observed in lower middle-income countries, as a result of the significant epidemic wave in India when the Delta variant emerged. This subsequently changed, with the greatest impact concentrated in higher-income countries in the second half of 2021, as restrictions on travel and social mixing were relaxed in some areas, leading to increased transmission of the virus.

Overall, the estimated number of deaths prevented per person was higher in high-income countries, reflecting the earlier and broader implementation of vaccination campaigns in these areas (66 deaths prevented per 10,000 people in high-income countries). high income vs. 2,711 deaths prevented per 10,000 people in high-income countries). low-income countries). High- and upper-middle-income countries accounted for the highest number of deaths prevented (12.2 million/19.8 million), highlighting inequalities in vaccine access around the world.

For the 83 countries included in the analysis that are covered by the COVAX commitment to affordable vaccines, approximately 7.4 million deaths were avoided out of a potential 17.9 million (41%). However, failure to meet the COVAX target of fully vaccinating 20% ​​of the population in some countries is estimated to have resulted in an additional 156,900 deaths. Although this figure represents a small proportion of total global deaths, these preventable deaths were concentrated in 31 African countries, where 132,700 deaths could have been avoided if the target had been met.

Similarly, the shortfall in the WHO’s goal of fully vaccinating 40% of each country’s population by the end of 2021 is estimated to have contributed to an additional 599,300 deaths worldwide that could have been avoided. LMICs accounted for the majority of these deaths (347,500/599,300 [59.7%]). Regionally, the majority of these deaths were concentrated in the African and Eastern Mediterranean regions (348,900/599,300 [58.2%] and 126,800/599,300 [21.2%] respectively). If the 40% target had been met in all low-income countries, the number of deaths averted by vaccination in these areas would have more than doubled (200,000 additional deaths averted on top of the estimated 180,300 deaths avoided with current vaccination rates).

Prof. Azra Ghani, Chair of Infectious Disease Epidemiology at Imperial College London: “Our study demonstrates the enormous benefit that vaccines had in reducing COVID-19 deaths globally. While the intense focus on the pandemic has now shifted, it is important that we ensure that the most vulnerable people in all parts of the world are protected from the continued circulation of COVID-19 and other major diseases that continue to disproportionately affect the poorest. Ensuring equitable access to vaccines is essential, but it requires more than simply donating vaccines. Improvements in vaccine infrastructure and distribution are needed, as well as coordinated efforts to combat vaccine misinformation and improve vaccine demand. Only then can we ensure that everyone has the opportunity to benefit from these life-saving technologies.”

The authors point out several limitations to their findings. In particular, their model is based on a number of necessary assumptions, including the precise proportions of the types of vaccines that have been delivered, how they were delivered, and the precise timing at which new variants of the virus arrived in each country. They also assumed that the relationship between age and the proportion of COVID-19 deaths occurring among infected people is the same for each country. More generally, the study’s findings should be considered in the context of uncertainty in estimating the true number of deaths from the pandemic due to the difference in reporting of COVID-19 mortality at the country level.

Writing in a linked comment, Professor Alison Galvani, who was not involved in the study, from the Yale University School of Public Health, US, said: "The saving of more than 19 million lives thanks to the "Unprecedented speed of development and COVID-19 vaccines are an extraordinary feat for global health. However, millions of additional lives could be saved through more equitable distribution of vaccines."

He added: "High coverage in an individual country not only benefits that country, but contributes to the global reduction in transmission and the emergence of new variants. A durable collective response is both pragmatic and ethically imperative."

The study was conducted by researchers at the Medical Research Council’s Center for Analysis of Global Infectious Diseases at Imperial College London, UK. It was funded by a Schmidt Scientific Fellowship in association with the Rhodes Trust, the World Health Organization, the UK Medical Research Council, the Gavi Foundation, Bill and Melinda Gates, the National Institute for Health Research and Community Jameel.