An estimated 20 million deaths worldwide were prevented by Covid-19 vaccines during the first year of the rollout, according to a new study in the Lancet.

The modelling research, published in The Lancet Infectious Diseases, is the first to assess how Covid-19 vaccines altered the course of the pandemic.

It found that 19.8 million out of a potential 31.4 million Covid-19 deaths were prevented worldwide according to estimates based on excess deaths from 185 countries and territories.

It also reviewed how inadequate access to vaccines in low-income countries has limited the impact in these settings, reinforcing the need for global vaccine equity and coverage.

High and upper-middle income countries accounted for the greatest number of prevented deaths (12.2 million/ 19.8 million), highlighting inequalities in access to vaccines around the world.

A further 599,300 deaths could have been averted if the World Health Organisation’s target of vaccinating 40% of the population in every country by the end of 2021 had been met.

One fifth of Covid-19 deaths in low-income countries could have been prevented

Dr Oliver Watson, lead author of the study, from Imperial College London, said: “Our findings offer the most complete assessment to date of the remarkable global impact that vaccination has had on the Covid-19 pandemic. Of the almost 20 million deaths estimated to have been prevented in the first year after vaccines were introduced, almost 7.5 million deaths were prevented in countries covered by the Covid-19 Vaccine Access initiative (COVAX).

"This initiative was set up because it was clear early on that global vaccine equity would be the only way out of the pandemic. Our findings show that millions of lives have likely been saved by making vaccines available to people everywhere, regardless of their wealth. However, more could have been done. If the targets set out by the WHO had been achieved, we estimate that roughly 1 in 5 of the estimated lives lost due to Covid-19 in low-income countries could have been prevented.”

The model accounted for variation in vaccination rates between countries, as well as differences in vaccine efficacy in each country based on the vaccine types known to have been predominately used in those areas. Notably, China was not included in the analysis owing to its large population and very strict lockdown measures, which would have skewed the findings.

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

Writing in a linked Comment, Professor Alison Galvani, who was not involved in the study, from Yale University School of Public Health, USA, said: "The saving of more than 19 million lives by the unprecedented rapidity of development and roll-out of Covid-19 vaccines is an extraordinary global health feat. Nonetheless, millions of additional lives could be saved by more equitable distribution of vaccines.

"High coverage in an individual country not only benefits that country but contributes to worldwide reduction in transmission and emergence of novel variants. An enduring collective response is both pragmatic and ethically imperative."