COVID-19: Relative Risk of Non-Vaccinated to Vaccinated Individuals

Area of Science:

• Public Health
• Epidemiology
• Vaccinology

Background:

• The COVID-19 pandemic prompted extensive vaccination campaigns globally, including in Italy for individuals aged 12 and above.
• Public and medical communities raised questions regarding the efficacy of vaccines against SARS-CoV-2, particularly concerning protection against infection versus severe disease.

Purpose of the Study:

• To quantify the effect of the COVID-19 vaccination campaign on various disease outcomes.
• To assess the relative risks of infection, hospitalization, intensive care admission, and death between vaccinated and unvaccinated individuals.

Main Methods:

• Calculated relative risks for non-vaccinated versus vaccinated individuals for all COVID-19 outcomes.
• Utilized likelihood ratios to compare the probability of outcomes in unvaccinated individuals relative to vaccinated individuals.

Main Results:

• Vaccination demonstrates a significant protective effect against critical COVID-19 conditions and death.
• The magnitude of protection appears greater against critical conditions than against death, suggesting a need for further research.

Conclusions:

• COVID-19 vaccination provides extensive protection, particularly against severe disease progression and mortality.
• The differential protective effect against critical illness versus death highlights areas for future investigation into vaccine mechanisms and impact.