The first worldwide estimate of the number of lives saved as a direct and indirect result of immunizations has been published.

Researchers used a mathematical model to estimate that 19.8 million lives were spared by the use of Covid-19 vaccines in the first year after their introduction. The study, which was conducted by a team of researchers at Imperial College London, UK, was published in The Lancet Infectious Diseases on Thursday, September 23.

The World Health Organization (WHO) estimated that 600,000 deaths may have been spared if 40% of the population in each nation had gotten two or more doses by the end of 2021.

According to projections made by Our World in Data, almost two-thirds of the world’s population has been immunized with at least one dosage of the vaccine since its first deployment in December 2020. More than 3.5 million fatalities were attributed to Covid-19 within the same time frame.

This is the first research to estimate how many lives have been saved as a direct and indirect result of immunizations worldwide. Up to that point, however, there have been attempts to quantify the effect of immunizations in particular geographic areas.

From December 8, 2020, to December 8, 2021, the team looked at data and estimations of fatalities and excess mortality from 185 nations. The term “excess mortality” is used to describe the difference between the projected number of fatalities if Covid-19 did not exist and the actual number of deaths connected with the pandemic.

Preventable fatalities ranged from 12.2 million to 19.8 million, with the largest numbers occurring in high- and upper-middle-income nations, indicating disparities in vaccination accessibility.

The vaccine effectiveness and vaccination rates in each country were included into the model. The authors state that the enormous population size and the implementation of stringent blocking measures in China were the primary reasons for excluding data from that country.

Based on one set of calculations made using official Covid-19 mortality statistics, the research found that 18.1 million lives may have been lost if a vaccine hadn’t been developed. In this case, it is believed that vaccination might have prevented 14.4 million fatalities, or 79%. This scenario does not take into account underreporting rates.

The information on the extra mortality was used to derive a new computation. Based on their research, the authors estimate that around 19.8 million lives were saved in the first year due to immunization. It prevented an estimated 31.4 million fatalities, a decrease of 63% when compared to the number of deaths that may have occurred in the absence of vaccination.

Between 15 and 19 million lives have been saved as a direct result of immunization protecting against fatal complications. Indirect protection, such as a decrease in viral transmission among the community and fewer patients requiring hospitalization, accounts for the remaining total, almost 4.3 million.

“Quantifying the worldwide effect of vaccination is difficult since availability to vaccinations differs across countries, as does our awareness of which coronavirus variants have been circulating, with relatively little genetic sequence data for different locations. In addition, it is impossible to know for sure how many people would have perished had vaccinations not been widely used. Gregory Barnsley, a researcher at Imperial College London and one of the study’s primary authors, explains that mathematical models are helpful for assessing hypothetical situations that are difficult to test in the actual world.

Professor Alison Galvani from Yale University’s School of Public Health in the United States, who was not involved in the study, said, “Saving more than 19 million lives by the unprecedented speed in the development and deployment of vaccines against Covid-19. 19 is an extraordinary achievement for global health.” But if vaccinations were distributed more fairly, millions of deaths may be spared.

“High vaccination coverage in one country helps that country and contributes to reducing transmission and the establishment of new variations throughout the globe. “A long-term communal reaction is both practically and morally necessary,” Galvani said.