Report published in prestigious Lancet journal notes more could have been saved if vaccination rates were higher
By THE LANCET
According to a new modeling study, published in The Lancet Infectious Diseases, COVID-19 vaccines are estimated to have prevented 20 million deaths worldwide in the first year of the vaccine program.
- First
modeling study to quantify the impact of COVID-19 vaccines
on a global scale estimates that 19.8 million out of a potential 31.4
million deaths were prevented in the first year after vaccines were
introduced (December 8, 2020 – December 8, 2021).
- 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.
- 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.
- 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 where official data was not available).
COVID-19 vaccines reduced the potential global
death toll during the pandemic by more than half in the year following their
implementation, according to estimates from a mathematical modeling study
published on June 23, 2022, in The Lancet Infectious
Diseases.
19.8 million out of a potential 31.4 million
COVID-19 deaths were prevented worldwide in the first year of the vaccination
program according to estimates based on excess deaths from 185 countries and
territories.
The researchers estimate that a further 599,300
lives could have been saved if the World Health
Organisation’s target of vaccinating 40% of the population
in each country with two or more doses by the end of 2021 had been met.
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. ”
Since the first COVID-19 vaccine was
administered outside of a clinical trial setting on December 8, 2020, almost
two-thirds of the world’s population has received at least one dose of a
COVID-19 vaccine (66%). The COVID-19 Vaccine Access initiative (COVAX) has
facilitated access to affordable vaccines for lower-income countries to try to reduce
inequalities, with an initial target of giving two vaccine doses to 20% of the
population in countries covered by the commitment by the end of 2021. The World
Health Organisation expanded this target by setting a global strategy to fully
vaccinate 70% of the world’s population by mid-2022, with an interim target of
vaccinating 40% of the population of all countries by the end of 2021.
Despite the incredible speed of the vaccine
roll-out worldwide, more than 3.5 million COVID-19 deaths have been reported
since the first vaccine was administered in December 2020.
Several studies have sought 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 vaccinations on a
global scale and the first to assess the number of deaths averted both directly
and indirectly.
Mr. Gregory Barnsley, co-first author of the
study, from Imperial College London, said: “Quantifying the impact that
vaccination has made globally is challenging because access to vaccines varies
between countries, as does our understanding of which COVID-19 variants have
been circulating, 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 vaccinations. Mathematical modeling offers a useful tool
for assessing alternative scenarios, which we can’t directly observe 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 occurring
between 8 December 2020 and 8 December 2021. To account for the under-reporting
of deaths in countries with weaker surveillance systems, they carried out a
separate analysis based on the number of excess deaths recorded above those
that would have been expected during the same time period. Where official data
was not available, the team used estimates of all-cause excess mortality. These
analyses were compared with an alternative hypothetical scenario in which no
vaccines were delivered.
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.
The team found that, based on officially
recorded COVID-19 deaths, an estimated 18.1 million deaths would have occurred
during the study period if vaccinations had not been implemented. Of these, the
model estimates that vaccination has prevented 14.4 million deaths,
representing a global reduction of 79%. These findings do not account for the
under-reporting of COVID-19 deaths, which is common in lower-income countries.
The team did a further analysis based on total excess deaths during the same
time period to account for this. They found that COVID-19 vaccination prevented
an estimated 19.8 million deaths out of a total of 31.4 million potential
deaths that would have occurred without vaccination, a reduction of 63%.
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.
Vaccine impact changed over time and in
different areas of the world as the pandemic progressed, the study found. In
the first half of 2021, the greatest number of deaths averted by vaccination
was seen in lower middle-income countries, resulting from the significant
epidemic wave in India as the Delta variant emerged. This subsequently shifted
to the greatest impact being concentrated in higher income countries in the
second half of 2021, as restrictions on travel and social mixing were eased in
some areas leading to greater virus transmission.
Overall, the number of estimated deaths
prevented per person was greatest in high-income countries, reflecting the
earlier and wider rollout of vaccination campaigns in these areas (66 deaths
prevented per 10,000 people in high-income countries vs 2.711 deaths prevented
per 10,000 people in low-income countries). High- and upper-middle-income
countries accounted for the greatest number of deaths averted (12.2 million/
19.8 million), highlighting inequalities in access to vaccines around the
world.
For the 83 countries included in the analysis
that are covered by the COVAX commitment to affordable vaccines, an estimated
7.4 million deaths were averted 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. Though
this figure represents a small proportion of the total global deaths, these
preventable deaths were concentrated in 31 African nations, where 132,700
deaths could have been averted if the target had been met.
Similarly, the shortfall in the WHO target of
fully vaccinating 40% of the population of each country by the end of 2021 is
estimated to have contributed to an additional 599,300 deaths worldwide that
could have been prevented. Lower-middle income countries accounted for the
majority of these deaths (347,500/599,300 [59.7%]). Regionally, most of these
deaths were focused in the Africa 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 prevented on top of the 180,300 deaths estimated to have been averted
under current vaccination rates).
Prof Azra Ghani, Chair in Infectious Disease
Epidemiology at Imperial College London: “Our study demonstrates the enormous
benefit that vaccines had in reducing deaths from COVID-19 globally. Whilst the
intense focus on the pandemic has now shifted, it is important that we ensure
the most vulnerable people in all parts of the world are protected from ongoing
circulation of COVID-19 and from the other major diseases that continue to
disproportionately affect the poorest. Ensuring fair access to vaccines is
crucial, but requires more than just donating vaccines. Improvements in vaccine
distribution and infrastructure, as well as coordinated efforts to combat
vaccine misinformation and improve vaccine demand, are needed. Only then can we
ensure that everyone has the opportunity to benefit from these life-saving
technologies.”
The authors note several limitations to their
findings. Notably, their model is based on a number of necessary assumptions,
including the precise proportions of which vaccine types have been delivered,
how they were delivered and the precise timing of when new virus variants
arrived in each country. They also assumed that the relationship between age
and the proportion of COVID-19 deaths occurring among infected individuals is
the same for each country. More broadly, the findings from the study should be
considered in the context of uncertainty in calculating the true death toll of
the pandemic owing to the difference in country-level reporting of COVID-19
mortality.
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.”
She added: “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.”
Reference: “Global impact of the first year of
COVID-19 vaccination: a mathematical modelling study” by Oliver J Watson, PhD;
Gregory Barnsley, MSc; Jaspreet Toor, PhD; Alexandra B Hogan, PhD; Peter
Winskill, PhD and Prof Azra C Ghani, PhD, 23 June 2022, The Lancet Infectious Diseases.
DOI:
10.1016/S1473-3099(22)00320-6
The study was carried out by researchers at the
Medical Research Council Centre for Global Infectious Disease Analysis at
Imperial College London, UK. It was funded by a Schmidt Science Fellowship in
partnership with the Rhodes Trust, World Health Organisation, UK Medical
Research Council, Gavi, Bill and Melinda Gates Foundation, National Institute
for Health Research and Community Jameel.
