Margaret Keenan, a 90-year-old British woman, received the first coronavirus vaccine outside of clinical trials. It was December 8, 2020, after an accelerated race never seen before in history to effectively protect against the virus. The study, published in the medical journal The Lancet, simulated what would happen in the world if it were not for vaccines, or better yet, how many lives they saved: 19.8 million people, as much as if covid had been transmitted. before the entire population of Ecuador or half of the Argentines. The work also confirms the inequality in the distribution of vaccinated between poor and rich countries.
Determining the impact of covid vaccines is not easy. Tests showed that they had between 60% and 90% (depending on the composition) of effectiveness, understood as a reduction in the risk of serious covid disease. But how many deaths have they prevented? It’s not easy to know. To do this, one would have to imagine two parallel worlds, one vaccinated and the other unvaccinated, and see where more people died from covid. Since such a comparison is impossible, one has to resort to mathematics and models. This is what researchers at Imperial College London (ICL) have done. Using demographic data, including comorbidities, from 185 countries, health infrastructure, previous infection rates, vaccination rates, and even vaccine types, they modeled their impact on the world from Margaret Keenan’s vaccination to December 8, 2021, just one year later.
If the model were based on covid death statistics, vaccines would have prevented the death of 14.4 million people in the 185 countries studied. But not everywhere there is reliable official data. Even in countries with advanced registration systems, as the case of Spain showed, the numbers did not reflect the real number of coronavirus deaths. Therefore, another way of counting them was introduced. All-cause mortality in 2020 or 2021 has been calculated and compared with mortality in pre-pandemic years. Thus, excess mortality may be related to the virus. With that in mind, Oliver Watson, research fellow at ICL’s Center for Global Infectious Disease Analysis and lead author of the study, makes it clear: “We estimate that nearly 20 million people would die in a world without vaccines.”
The map shows the number of deaths that the study estimated were prevented by vaccines per 10,000 people in the population. The authors excluded China from the analysis.Watson et al./Nature
According to the model, the vast majority of averted deaths were due to the direct effects of the vaccine, i.e. through immunization. The rest will be associated with indirect effects: herd immunity and reduced burden on the healthcare system. The impact of various vaccines was hardly noticed until mid-2021, when dual guidance was already completed in the most advanced countries in the field of vaccination, but most restrictions were lifted. This study also shows differences, sometimes huge, between some countries and others.
“Of the nearly 20 million estimated avoidable deaths in the first year of vaccines, about 7.5 million occurred in countries covered by the Covid Vaccine Access Initiative (Covax, an abbreviation in English),” says Watson. This mechanism, promoted by the UN, WHO and the GAVI Vaccine Alliance, had as its mission the most equal access and possible distribution among different countries.Covax set a goal to vaccinate at least 20% of the population of the hundred poorest countries by the end of 2021. WHO was even more ambitious, raising that target to 40%, but the reality was different: for example, the first vaccine arrived in Burundi 10 months later than in the United States, while the US government had already purchased enough vaccines to vaccinate its entire population three times schedule, before they became available, only 0.07% of people in the Democratic Republic of the Congo received at least one dose at the end of 2021.
The time factor has been shown to be key. Vaccination began in Europe, the US, Canada and other developed countries much earlier than in the rest of the world, and in droves. “This meant that as transmission increased in 2021, more deaths were averted, either by relaxing non-drug interventions or by introducing a more contagious Delta variant in the second half of the year. If vaccination had been provided before and before the availability of this option in low-income countries, more lives would have been saved, ”comments the British researcher. “Had the targets set by the WHO been met, we estimate that about one in five lives could be averted from COVID-19 in less developed countries,” Watson said.
“Had the targets set by the WHO been met, we estimate that the loss of about one in five lives from COVID-19 in less developed countries could be avoided.”
Oliver Watson, Research Fellow, Center for Global Analysis of Infectious Diseases, Imperial College London
The work also confirms that not all vaccines are the same. In countries where vaccines based on RNA technology (from Moderna and Pfizer) had the weight of vaccination, the number of lives saved was greater. In addition to being more effective, especially with the Delta variant, these vaccines require tighter storage and transport conditions, meaning they barely reach many of those countries that are already penalized for delaying any vaccine. But the model also revealed relatively lower vaccination readiness in many Covax countries and insufficient infrastructure to scale up vaccination efforts in their residents.
Professor Azra Ghani, head of infectious disease epidemiology at Imperial College London, highlights this in a note: “Our study demonstrates the enormous benefit that vaccines have had in reducing Covid deaths worldwide. While the focus on the pandemic has 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 the disease…Ensuring equal access to vaccines is critical, but it requires more than just giving up vaccines. Improvements in infrastructure and distribution are needed, as well as a coordinated effort to combat misinformation about vaccines. Only then can we ensure that everyone has the opportunity to benefit from these vital technologies.”
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