The COVID-19 pandemic has had major health, economic and social implications, bringing
with it a large number of deaths worldwide. While the lethality rate could not be
considered high, the fact that the contagiousness was high resulted in a considerable
number of deaths. As a result, the COVID-19 pandemic has become a sudden, huge and urgent
public health problem.

Initially faced with a new and unknown etiopathological entity, different countries
adopted different policies that proved more or less effective in containing the COVID-19
contagion. While social and hygienic restrictive measures (i.e. so-called social
distancing, curfews, use of masks and hand hygiene) initially had a positive impact on
reducing infections, for the most part they proved to be ephemeral measures. These
actions were short-lived because they were not sustainable over time due to the damage
they implied with regard to mental health, besides the low adherence of the population. A
relaxation of these restrictive measures has always led to an increase in the spread of
the COVID-19 pandemic, with a resurgence of hospital admissions, an ever-increasing
occupancy of intensive care beds and a subsequent increase in the number of deaths.

Since the beginning of the COVID-19 pandemic, scientific research has been working to
enable the identification of the SARS-CoV-2 viral genome and possible target proteins for
treatment. Due to years of vaccine research and the launch of Access to COVID-19 Tools
(ACT)-Accelerator partnership, a rapid development of several candidate vaccines based on
different vaccine technologies and thus to their rapid clinical testing were possible.

Thanks also to the regulatory agencies' solicitude, in certain Countries (e.g. Israel,
the UK, the US and the EU) the COVID-19 vaccination campaign started at the end of 2020
and extended worldwide during 2021 (with the exception of Eritrea and the Democratic
Republic of Korea).

Through purchasing agreements with individual vaccine manufacturers, governments (or
supranational institutions, e.g. the EU) secured the supply of the necessary doses.
However, this entailed a division of the world's population depending on the negotiating
power of the country of residence and, therefore, its economic strength. COVAX is one of
the three pillars of the ACT-Accelerator programme: dedicated to vaccines, the purpose of
COVAX is to accelerate the development and manufacture of COVID-19 vaccines, ensuring
fair and equitable access for every country in the world.

In a globalised world, guaranteeing everyone the right to health is mandatory from a
moral as well as an economic and global health point of view: everyone gains if the
poorest improve their condition (think infectious diseases). In a globalised world, it is
necessary to 'globalise' health and not only the economy: this study aims to understand
where governments, supranational institutions and non-governmental organisations can act
more incisively to combat the COVID-19 pandemic with the weapon the vaccine represents.

On this basis, the investigators decided to examine whether certain variables could be
determinants of vaccination coverage for COVID-19. Two outcomes were identified as
indicators of vaccination coverage: the proportion of the population vaccinated with at
least one dose and the ratio of administered doses to the population. These data were
obtained from the COVID-19 dataset by Our World In Data as of 15th June for each country.
If data was not available on that date, the most recent available data was used looking
retrospectively. In order to analyze whether and which were determinants of vaccination
coverage, several variables are accounted: socio-demographic variables: total population,
population density, median age, GINI Index; economic variables: GDP per capita; health
variables: COVID-19-specific mortality, type of health system (public or private), health
personnel (Physicians /1000 population, Nurses and midwives personnel/1000 population);
cultural variables (literacy rate, Greenberg Index, presence of a predominant religion),
infrastructural variables (density of road network, access to electricity) and political
variables (civil liberties, political stability and absence of violence/terrorism). Data
for the aforementioned variables were extracted from institutional databases/ datasets:
World Bank, Our World In Data, World Religion Database and The World Factbook. For
Greenberg Index, as proxy of Cultural Diversity Index, the data were from Gören (2018),
taking the 2020 figure for each country, or the most recent available figure if the 2020
figure is not available.

Statistical analyses will be conducted including all countries in the world taken
individually, for which vaccination data are available as of 15 June 2022. In addition,
analyses will also be conducted for outcomes adjusted for vaccine doses delivered (in
each country). The data for this correction factor were obtained from the UNICEF database
on 21th June 2022.

Statistical analyses by subgroups will also be implemented, stratifying by World Bank
country classification by income level: High, Upper-middle, Lower-middle, Low.