Covid-19: vaccines would have avoided nearly 20 million deaths in 2021

Vaccination against Covid-19 averted 19.8 million deaths out of a potential 31.4 million in the year following the introduction of the vaccines (between December 2020 and December 2021), announces a modeling studypublished this June 23 in The Lancet Infectious Diseases. This is the first work to assess the deaths averted directly and indirectly through vaccination on a global scale.

To arrive at this result, the authors relied on data from 185 countries and territories, using each country’s excess death records (which is the gap between the number of people who died – regardless of cause of death – and the number of deaths expected according to statistics from previous years), or estimates when official data were not available. These analyzes were compared to an alternative hypothetical scenario in which no vaccine would have been administered.

The model also accounted for variation in vaccination rates across countries, as well as differences in vaccine effectiveness in each country based on the types of vaccines known to have been primarily used in those countries. regions. Note that China was not included in the analysis due to its large population and very strict containment measures, which would have distorted the results.

One in five deaths could have been avoided with better access to the vaccine

Conclusions: Covid-19 vaccines more than halved the potential number of deaths worldwide within a year of their introduction. High- and middle-income countries recorded the highest number of deaths averted (12.2 million out of 19.8 million), which reflects the earlier and wider deployment of vaccination campaigns in these regions and also highlights inequalities in access to vaccines around the world. Nearly 7.5 million deaths have been averted in countries covered by the Covid-19 vaccine access initiative (Covax).

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Scientists further estimate that nearly 600,000 deaths could have been prevented if the World Health Organization (WHO) target of achieving vaccination coverage of 40% of the population in each country by the end of 2021 had been reached.

“Our results show that millions of lives were likely saved by making vaccines available to everyone, regardless of wealth,” said Oliver Watson, researcher at Imperial College London and lead author of the study, in a press release published by the scientific journal. However, we could have done more. If the targets set by the WHO had been met, we estimate that around one in five deaths linked to Covid-19 could have been prevented in low-income countries.

More than three quarters (or 15.5 million out of 19.8 million) of the deaths averted were due to the direct protection provided by vaccination against severe symptoms, leading, de facto, to lower mortality rates. The remaining 4.3 million deaths averted were, according to the authors, through indirect protection due to reduced transmission of the virus in the population and reduced burden on health systems, which improved access to medical care for those most in need.

Working on misinformation

The authors point out a number of limitations. Faced with global disparities in genomic surveillance of SARS-CoV-2 and given the lack of detailed data on vaccination in the majority of countries, they had to base their model on a number of assumptions of work. In particular around the vaccines administered, the way in which they were as well as the moment when the new worrying variants spread in the world. The researchers also assumed that the relationship between age and the proportion of Covid-19 deaths occurring among infected people was the same for each country studied. More generally, the results of the study must be considered in a context of uncertainty surrounding the true calculation of the toll of the pandemic, due to the difference in the reporting of mortality due to Covid-19 at the level of the countries.

Impact estimates also depended on the assumed degree of immune escape from each variant. “If immune escape was higher than we assumed, more of the population would have been susceptible to re-infection and therefore more deaths from Covid-19 could have been prevented. by vaccination,” the authors write in their study. Before adding: “The results of this analysis nevertheless provide a complete and thorough assessment of the impact of vaccination against Covid-19, revealing the substantial impact of vaccines and the millions of lives that have probably been saved during of the first year of vaccination.

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“It is important that we ensure that the most vulnerable people in all regions of the world are protected from the continued circulation of Covid-19 and other major diseases which continue to disproportionately affect the poorest, concludes the professor. Azra Ghani, chair of infectious disease epidemiology at Imperial College and co-author of the study. Ensuring equitable access to vaccines is essential, but donating vaccines is not enough. Their distribution and infrastructure need to be improved, just as coordinated efforts are needed to counter misinformation about vaccines and increase demand for them. Only then can we ensure that everyone has the opportunity to benefit from these life-saving technologies.”

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