Influenza vaccination is routinely offered each year to several groups, including all adults in England aged 65 years or older, and younger adults with medical conditions such as diabetes and heart disease. In 2020/21 and 2021/22 this was widened to all adults over 50 years as a temporary measure due to the COVID-19 pandemic . Within these groups, uptake of vaccine is suboptimal and varies by medical condition. Within these groups, it is unclear whether people known to be at high clinical risk of severe influenza are more or less likely to be unvaccinated, or whether uptake can be increased through age-based eligibility or vaccination in outpatient clinics.
The study will use anonymised GP and hospital records to describe influenza vaccination among adults eligible for flu vaccine due to age or underlying health conditions in the 2018/19, 2019/20 and 2020/21 flu seasons. It will explore whether people with indicators that they are at higher risk of severe flu (such as a history of being admitted to hospital with flu, having more than one health condition, or markers of severe disease for diabetes and liver disease) are more or less likely to receive the flu vaccine. It will also explore whether increasing the age range of flu vaccination in 2020/21 increased uptake among people aged 50 to 64 years with medical conditions from 2019/20, compared to the change in vaccine uptake for close age groups in the same time period, and describe uptake of flu vaccination among people who attend outpatients.
All adults in England aged 65 years or older, and younger adults with underlying health conditions (e.g. diabetes) are eligible for annual seasonal influenza vaccine. For 2020/21 and 2021/22 this was temporarily widened to all adults aged 50 years or older. Influenza vaccine uptake among over 65s is below the 75% recommended by the World Health Organization, and varies by medical condition among younger adults, with low uptake among high-risk groups such as people with liver disease. Within these groups, it is unclear whether people known to be at particularly high risk of severe influenza are more or less likely to receive influenza vaccine. It is also unclear whether routine flu vaccine uptake can be improved by wider age-based eligibility, or vaccination in outpatient clinics.
This cohort study will use CPRD Aurum with linked hospital episode statistics inpatient and outpatient data to describe influenza vaccine uptake in each of the flu seasons 2018/19, 2019/20 and 2020/21. Multivariable logistic regression models will be used to explore whether markers of a higher risk of severe influenza are associated with vaccine uptake, examining multimorbidity, and hospital admission for any cause in the last year, or any history of hospitalisation for acute respiratory infection. Disease-specific markers of clinical severity will also be explored focusing on diabetes mellitus, and chronic liver disease.
Among adults with underlying health conditions, we will explore the impact of age-based eligibility for 50–64-year-olds in 2020/21 using a ratio-of-ratios approach to compare the ratio of vaccine uptake in 2020/21 to 2019/20 for 50–64-year-olds compared to the same ratio among adults aged 45–49 years, and 65–69 years. Finally, we will describe influenza vaccine uptake according to outpatient attendance in the previous influenza season, and the commonest outpatient specialties attended by people who are eligible for vaccination and unvaccinated.
Influenza vaccine uptake within the period 1 September to 28 February for each year: 2018/19, 2019/20, 2020/21.
Kathryn Mansfield - Chief Investigator - London School of Hygiene & Tropical Medicine ( LSHTM )
Kathryn Mansfield - Corresponding Applicant - London School of Hygiene & Tropical Medicine ( LSHTM )
Emily Graul - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Jemma Walker - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
Kathryn Mansfield - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )
HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation