# Influenza Vaccination in Children During the First Two Seasons of Routine Vaccination Programs (2023–24 and 2024–25) in Central Catalonia, Spain: A Retrospective Study

## TL;DR

This study examines how well children in Spain were vaccinated against the flu during the first two years of a new vaccination program and finds that coverage and adherence remain low.

## Contribution

The study provides new insights into influenza vaccination coverage and adherence in children under 5 years and those with chronic conditions in Spain.

## Key findings

- Influenza vaccination coverage in children was 18.1% and 19.3% in the 2023–24 and 2024–25 seasons, respectively.
- Adherence to vaccination across both seasons was only 17%.
- Factors like immigrant origin, urban residence, and multiple risk factors were associated with vaccination.

## Abstract

Public health relevance—How does this work relate to a public health issue?
The World Health Organization (WHO) estimates that every year 1 billion people contract the flu, of which 3–5 million have serious symptoms and the number of deaths from respiratory diseases related to influenza infection is between 290,000 and 650,000.In Spain, from the 2023–2024 season, the influenza vaccine has become part of the routine vaccination program for children from 6 to 59 months.

The World Health Organization (WHO) estimates that every year 1 billion people contract the flu, of which 3–5 million have serious symptoms and the number of deaths from respiratory diseases related to influenza infection is between 290,000 and 650,000.

In Spain, from the 2023–2024 season, the influenza vaccine has become part of the routine vaccination program for children from 6 to 59 months.

Public health significance—Why is this work of significance to public health?
This work assesses the coverage and the adherence of influenza vaccination in children after the introduction of the influenza vaccine into the routine vaccination program in Spain for children under 5 years of age.It also attempts to identify the risk factors associated with influenza vaccination in all age groups (under 5 years and from 5 to 14 years with chronic pathologies).

This work assesses the coverage and the adherence of influenza vaccination in children after the introduction of the influenza vaccine into the routine vaccination program in Spain for children under 5 years of age.

It also attempts to identify the risk factors associated with influenza vaccination in all age groups (under 5 years and from 5 to 14 years with chronic pathologies).

Public health implications—What are the key implications or messages for practitioners, policy makers and/or researchers in public health?
Both the coverage and the adherence to influenza vaccination in children are very low, despite the introduction of a routine influenza vaccination program in children from 6 to 59 months.Factors associated with influenza vaccination in children aged 6–59 months included immigrant origin, urban residence, the presence of multiple risk factors, and specific underlying chronic conditions.

Both the coverage and the adherence to influenza vaccination in children are very low, despite the introduction of a routine influenza vaccination program in children from 6 to 59 months.

Factors associated with influenza vaccination in children aged 6–59 months included immigrant origin, urban residence, the presence of multiple risk factors, and specific underlying chronic conditions.

Vaccination is the primary method of preventing influenza. During the 2023–24 season, the influenza vaccination for all children between 6 and 59 months was introduced for the first time in Spain. To assess the coverage and adherence of influenza vaccination in childhood during the first two seasons of a vaccination program, as well as to identify the factors associated with influenza vaccination in all children under 5 years of age and those from 5 to 14 years of age with risk factors. Retrospective observational study. All children eligible for the flu vaccine in Central Catalonia during the 2023–24 and 2024–25 seasons were included. A total of 39,937 children were studied. Of these, 79.1% had not been vaccinated for influenza in either of the seasons studied. Influenza vaccination coverage in childhood was 18.1% and 19.3% in the 2023–24 and 2024–25 seasons, respectively. In the 6- to 59-month age range, coverage was 19.1% and 28.9% in the 2023–24 and 2024–25 seasons, respectively. The adherence to vaccination in both seasons was 17%. Some variables (being a non-native person, living in an urban area, having more than one risk factor, or certain underlying conditions) were associated with the influenza vaccination. Coverage and adherence to influenza vaccination in childhood are very low, despite the implementation of a routine influenza vaccination program.