Relative effectiveness of the adjuvanted vs non-adjuvanted seasonal influenza vaccines against severe laboratory-confirmed influenza among hospitalized Italian older adults. (December 2022)

• Record Type: Journal Article
• Authors: Domnich, Alexander; Panatto, Donatella; Pariani, Elena; Napoli, Christian; Chironna, Maria; Manini, Ilaria; Rizzo, Caterina; Orsi, Andrea; Icardi, Giancarlo
• Is Part Of: International journal of infectious diseases. Volume 125(2022)
• Page Start: 164
• Page End: 169
• Publication Date: 2022-12
• Subjects: Influenza -- Influenza vaccines -- Adjuvanted influenza vaccine -- Vaccine effectiveness -- Older adults; Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2022.10.041
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: Both adjuvanted trivalent (aTIV) and unadjuvanted quadrivalent (QIVe) flu vaccines are used in older adults. It is largely unknown if aTIV is more effective than QIVe against confirmed influenza. aTIV was more effective than QIVe against severe laboratory-confirmed influenza. The relative effectiveness of aTIV vs QIVe may be biased by confounding by indication. ABSTRACT: Objectives: In this study, we aimed to investigate the relative vaccine effectiveness (rVE) of the MF59-adjuvanted trivalent (aTIV) and non-adjuvanted quadrivalent (QIVe) egg-based standard-dose vaccines against severe laboratory-confirmed influenza. Methods: This test-negative case-control study was conducted in a hospital setting during four recent Italian influenza seasons (from 2018/19 to 2021/22). The clinical outcome was severe acute respiratory infection (SARI) with laboratory confirmation diagnosed among subjects aged ≥65 years. rVE of aTIV versus QIVe was estimated through propensity score matching followed by logistic regression. Results: The influenza virus circulated to a significant extent only during the 2018/19 and 2019/20 seasons. The final population included 512 vaccinated older adults, of which 83 were cases and 429 were test-negative controls. aTIV and QIVe users differed substantially from the point of view of several baseline characteristics. The propensity score adjusted rVE of aTIV vs QIVe was 59.2% (95% CI: 14.6%, 80.5%), 54.7% (95% CI: -28.7%, 84.0%) and 56.9% (95% CI: -7.8%, 82.8%) against any influenza, A(H1N1)pdm09 and A(H3N2), respectively. Conclusion: aTIV was more effective than QIVe in preventing laboratory-confirmed SARI. The benefits of aTIV may be obscured by confounding indication.