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Within influenza vaccine effectiveness (VE) studies at primary care level with a laboratory-confirmed outcome, clinical case definitions for recruitment of patients can vary. We used the 2022–23 VEBIS primary care European multicentre study end-of-season data to evaluate whether the clinical case definition affected IVE estimates. We estimated VE using a multicentre test-negative case-control design. We measured VE against any influenza and influenza (sub)types, by age group (0–14, 15–64, ≥65 years) and by influenza vaccine target group, using logistic regression. We estimated IVE among patients meeting the European Union (EU) acute respiratory infection (ARI) case definition and among those meeting the EU influenza-like illness (ILI) case definition, including only sites providing information on specific symptoms and recruiting patients using an ARI case definition (as the EU ILI case definition is a subset of the EU ARI one). We included 24 319 patients meeting the EU ARI case definition, of whom 21 804 patients (90 %) meet the EU ILI case definition, for the overall pooled VE analysis against any influenza. The overall and influenza (sub)type-specific VE varied by ≤2 % between EU ILI and EU ARI populations. Among all analyses, we found similar VE estimates between the EU ILI and EU ARI populations, with few (10%) additional non-ILI ARI patients recruited. These results indicate that VE in the 2022–23 influenza season was not affected by use of a different clinical case definition for recruitment, although we recommend investigating whether this holds true for next seasons. [ABSTRACT FROM AUTHOR]

As the COVID-19 pandemic progressed, so too did the proportion of cases admitted to critical care in Ireland who were fully vaccinated. Reporting of this observation has public health implications as incorrect interpretation may affect public confidence in COVID-19 vaccines. A potential explanation is the reduced ability of those who are immunocompromised to produce an adequate, sustained immune response to vaccination. We conducted an analysis of the association between COVID-19 vaccination status and underlying degree of immunocompromise among a cohort of critical care patients all with a confirmed diagnosis of COVID-19 admitted to critical care between July and October 2021. Multinomial logistic regression was used to estimate an odds ratio of immunocompromise among vaccinated COVID-19 cases in critical care compared to unvaccinated cases. In this study, we found a statistically significant association between the vaccination status of severe COVID-19 cases requiring critical care admission and underlying immunocompromise. Fully vaccinated patients were significantly more likely to be highly (OR = 19.3, 95 % CI 7.7–48.1) or moderately immunocompromised (OR = 9.6, 95 % CI 5.0–18.1) compared to unvaccinated patients with COVID-19. These findings support our hypothesis, that highly immunocompromised patients are less likely to produce an adequate and sustained immune response to COVID-19 vaccination, and are therefore more likely to require critical care admission for COVID-19 infection. [ABSTRACT FROM AUTHOR]

• Seasonal influenza vaccine programmes usually target at-risk and older individuals. • We used an age-structured dynamic-transmission model for eight European settings. • Older people benefit from adjuvanted or high-dose trivalent or quadrivalent vaccines. • Adopting mass paediatric influenza vaccination is also likely to be cost-effective. • Results rest on vaccine costs, willingness to vaccinate and unknown long-term effects. Despite seasonal influenza vaccination programmes in most countries targeting individuals aged ≥ 65 (or ≥ 55) years and high risk-groups, significant disease burden remains. We explored the impact and cost-effectiveness of 27 vaccination programmes targeting the elderly and/or children in eight European settings (n = 205.8 million). We used an age-structured dynamic-transmission model to infer age- and (sub-)type-specific seasonal influenza virus infections calibrated to England, France, Ireland, Navarra, The Netherlands, Portugal, Scotland, and Spain between 2010/11 and 2017/18. The base-case vaccination scenario consisted of non-adjuvanted, non-high dose trivalent vaccines (TV) and no universal paediatric vaccination. We explored i) moving the elderly to "improved" (i.e., adjuvanted or high-dose) trivalent vaccines (iTV) or non-adjuvanted non-high-dose quadrivalent vaccines (QV); ii) adopting mass paediatric vaccination with TV or QV; and iii) combining the elderly and paediatric strategies. We estimated setting-specific costs and quality-adjusted life years (QALYs) gained from the healthcare perspective, and discounted QALYs at 3.0%. In the elderly, the estimated numbers of infection per 100,000 population are reduced by a median of 261.5 (range across settings: 154.4, 475.7) when moving the elderly to iTV and by 150.8 (77.6, 262.3) when moving them to QV. Through indirect protection, adopting mass paediatric programmes with 25% uptake achieves similar reductions in the elderly of 233.6 using TV (range: 58.9, 425.6) or 266.5 using QV (65.7, 477.9), with substantial health gains from averted infections across ages. At €35,000/QALY gained, moving the elderly to iTV plus adopting mass paediatric QV programmes provides the highest mean net benefits and probabilities of being cost-effective in all settings and paediatric coverage levels. Given the direct and indirect protection, and depending on the vaccine prices, model results support a combination of having moved the elderly to an improved vaccine and adopting universal paediatric vaccination programmes across the European settings. [ABSTRACT FROM AUTHOR]

The World Health Organization (WHO), and European Agencies recommend influenza vaccination for individuals at-risk due to age (≥65 years), underlying diseases, pregnancy and for health care workers (HCWs) in Europe. Pneumococcal vaccine is recommended for those at-risk of pneumococcal disease. In Ireland, vaccination uptake among at-risk adults is not routinely available. In 2013, we conducted a national survey among Irish residents ≥18 years of age, to estimate size and vaccination coverage of at-risk groups, and identify predictive factors for influenza vaccination. We used computer assisted telephone interviews to collect self-reported information on health, vaccination status, attitudes towards vaccination. We calculated prevalence and prevalence ratios (PR) using binomial regression. Overall, 1770 individuals participated. For influenza, among those aged 18–64 years, 22% (325/1485) [95%CI: 17%–20%] were at-risk; 28% [95%CI: 23%–33%] were vaccinated. Among those aged ≥65 years, 60% [95%CI: 54%–66%] were vaccinated. Influenza vaccine uptake among HCWs was 28% [95%CI: 21%–35%]. For pneumococcal disease, among those aged 18–64 years, 18% [95%CI: 16%–20%] were at-risk; 16% [95%CI: 12%–21%] reported ever-vaccination; among those aged ≥65 years, 36% [95%CI: 30%–42%] reported ever-vaccination. Main reasons for not receiving influenza vaccine were perceptions of not being at-risk, or not thinking of it; and among HCWs thinking that vaccination was not necessary or they were not at-risk. At-risk individuals were more likely to be vaccinated if their doctor had recommended it (PR 3.2; [95%CI: 2.4%-4.4%]) or they had access to free medical care or free vaccination services (PR 2.0; [95%CI: 1.5%-2.8%]). Vaccination coverage for both influenza and pneumococcal vaccines in at-risk individuals aged 18–64 years was very low. Influenza vaccination coverage among individuals ≥65 years was moderate. Influenza vaccination status was associated with GP vaccination recommendation and free access to vaccination services. Doctors should identify and recommend vaccination to at-risk patients to improve uptake. [ABSTRACT FROM AUTHOR]