Uptake of the Childhood Live Attenuated Influenza Vaccine (LAIV) and Influenza-related Healthcare Resource Use in England During the 2012 to 2022 Flu Seasons; a Retrospective, Observational Study in the CPRD and HES Databases

Study Overview
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Brief Summary
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In 2013, the NHS started a vaccination program in some regions of England to provide free flu vaccines to children aged 2 years or older, and younger than 16 years. The program has since been rolled out across England. Most children are given a vaccine that is sprayed into their nose. In clinical trials, this vaccine has been shown to protect children from experiencing severe flu symptoms. It is important to describe how it is used, and what happens to children who receive it in the wider community. This evidence will help the NHS to check that the vaccine roll out runs as planned and produces the intended benefits. This study aims to: (1) describe how many children each year receive flu vaccines, and describe the characteristics of children who are and aren't vaccinated for influenza; (2) test how often children receiving the vaccine see their GP or a hospital doctor for symptoms related to flu, compared to those who don't; and (3) to test what groups of children are more or less likely to receive a flu vaccine. To answer these objectives, the study will use the Clinical Practice Research Datalink, linked to Hospital Episode Statistics and the Office for National Statistics database.

Detailed Description
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A Live Attenuated Influenza Vaccination (LAIV) has been offered to children through a rolling national program in England since 2013. Previous observational studies identified trends in LAIV uptake that varied with demographic and clinical profiles. The general aim of this study is to provide up-to-date epidemiological evidence on the uptake of the influenza vaccines, and influenza related HCRU outcomes in children in England. The specific study objectives are given below. Primary objective: 1. To evaluate the uptake of influenza vaccines in children aged ≥2 and <18 years in England between 2012 and 2020 for LAIV, QIV, and influenza vaccinations where the product is not specified Secondary objectives: 2.1 To describe usage patterns of LAIV in England between 2012 and 2020. 2.2 To describe HCRU associated with laboratory confirmed influenza and/or influenza-like-illness (ILI) in England between 2012 and 2020 and assess the relative impact of LAIV on HCRU use of LAIV vs no vaccination 2.3 To describe demographics and clinical characteristics of individuals vaccinated with LAIV or not vaccinated against flu by any vaccine in each flu season between 2012 and 2020 2.4 To estimate a DAG aligned model for LAIV uptake in England based on demographic and clinical factors for each flu season and across multiple seasons between 2012 and 2020 The study will include all research eligible aged between ≥2 and <18 years in the study period, with 6 months of history in CPRD before their first influenza vaccination. It will use the Clinical Practice Research Datalink data (vaccinations, diagnoses, characteristics) linked to Hospital Episode Statistics (HCRU). Logistic regression analyses will be used to test for factors associated with vaccine uptake, and outcomes between vaccinated and unvaccinated children. The study will provide up-to-date epidemiological evidence on the uptake of LAIV and its impact on HCRU related to ILI in children in England. This may be used by the NHS for planning and evaluation of the childhood influenza vaccination program.

Official Title
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Uptake of the Childhood Live Attenuated Influenza Vaccine (LAIV) and Influenza-related Healthcare Resource Use in England During the 2012 to 2022 Flu Seasons; a Retrospective, Observational Study in the CPRD and HES Databases

Conditions
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Influenza

Participation Criteria
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Eligibility Criteria
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The reference study cohort will include patients as follows: Aged ≥2 and <18 years at any time between 1 September 2012 and 30 April 2020 Classified as eligible for inclusion in research analysis according to CPRD guidance In each flu season, the following criteria apply: Inclusion Criteria: Aged ≥6 months and <2 years on the 1st September Have a high-risk condition as listed in the Green Book. Exclusion Criteria: Were deceased or had migrated out of their practice prior to the 1st September in the current influenza season. Were recorded has receiving both QIV and LAIV in the current influenza season.

Ages Eligible for Study
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Minimum Age: 0 Years
Maximum Age: 17 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| LAIV Vaccinated cohort<br>All individuals receiving LAIV between 2 and <18 years within a given flu season between 2012 and 2020. | |
| Unvaccinated cohort<br>All individuals between 2 and <18 years with no record of influenza vaccinations in a given flu season | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Uptake of influenza vaccination | Proportion of eligible individuals receiving a flu vaccine (LAIV, QIV, other) | Per flu season (defined as 1st September in a given year to the 30th April the following year ) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| GP consultations for ILI (influenza-like illness) | Rate of GP consultations for ILI per 100,000 person years. | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Laboratory confirmed influenza | Rate of Laboratory confirmed influenza for ILI per 100,000 person years. | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Admitted Patient Care (APC) episodes associated with ILI | Rate of Admitted Patient Care (APC) for ILI per 100,000 person years. | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Accident and Emergency (A&E) attendances associated with ILI | Rate of A&E for ILI per 100,000 person years. | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Outpatient attendances associated with ILI | Rate of Outpatient attendances associated with ILI per 100,000 person years. | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Length of stay in APC for influenza and ILI | Average length of stay in hospital for influenza and ILI | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Number of antibiotic prescriptions | Counts of antibiotic prescriptions | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). | 
| Number of antiviral prescriptions | Counts of antiviral prescriptions | From vaccination date until the earliest of death, de-registration, or the end of the influenza season (30th April of the second calendar year the season spans). |