BY-COVID - WP5 - Baseline Use Case: SARS-CoV-2 vaccine effectiveness assessment preliminary outputs from Aragon, Spain

This publication corresponds to the preliminary outputs for the Baseline Use Case proposed in T.5.2 (WP5) in the BY-COVID project on "SARS-CoV-2 Vaccine(s) effectiveness in preventing SARS-CoV-2 infection" in Aragon, Spain.

Research Question: "How effective have the SARS-CoV-2 vaccination programmes been in preventing SARS-CoV-2 infections?"

• Intervention (exposure): COVID-19 vaccine(s) 
• Outcome: SARS-CoV-2 infection 
• Subgroup analysis: Vaccination schedule (type of vaccine)

Study Design: An observational retrospective longitudinal study to assess the effectiveness of the SARS-CoV-2 vaccine in preventing SARS-CoV-2 infections using routinely collected social, health and care data from several countries.

A causal model was established using Directed Acyclic Graphs (DAGs) to map domain knowledge, theories and assumptions about the causal relationship between exposure and outcome. The DAG developed for the research question of interest is shown below.

Cohort definition: All people eligible to be vaccinated (from 5 to 115 years old, included) or with, at least, one dose of a SARS-CoV-2 vaccine (any of the available brands) having or not a previous SARS-CoV-2 infection.

• Inclusion criteria: All people vaccinated with at least one dose of the COVID-19 vaccine (any available brands) in an area of residence. Any person eligible to be vaccinated (from 5 to 115 years old, included) with a positive diagnosis (irrespective of the type of test) for SARS-CoV-2 infection (COVID-19) during the period of study.
• Exclusion criteria: People not eligible for the vaccine (from 0 to 4 years old, included)
• Study period: From the date of the first documented SARS-CoV-2 infection in each country to the most recent date in which data is available at the time of analysis, roughly from 01-03-2020 to 30-06-2022, depending on the country. 

Outcome: Time from primary vaccination to confirmed SARS-CoV-2 infection. 

These outputs correspond with the interactive reports of each main step of the analytical pipeline described in 'Methods analytical pipeline' and have been produced using routinely collected data from public health and the national health system in the region of Aragon (Spain) with population coverage (~1.3 million lives). 

The scripts implementing the statistical analyses in the analytical pipeline are available on GitHub, with additional documentation supporting the development and implementation of the baseline use case.