Adjuvanted versus non-adjuvanted standard-dose influenza vaccines in preventing all-cause hospitalizations in the elderly: a cohort study with nested case-control analyses over 18 influenza seasons

ABSTRACT

Background

The higher effectiveness of adjuvanted trivalent influenza vaccine (aTIV) versus non-adjuvanted (na) formulations in preventing all-cause hospitalization has been demonstrated for a single influenza season and in institutionalized elderly only. This study evaluated the relative vaccine effectiveness for aTIV vs. non-adjuvanted trivalent (naTIV) and/or quadrivalent (naQIV) influenza vaccines in preventing all-cause hospitalizations across 18 influenza seasons in primary care.

Research design and methods

Using Health Search Database, a nested case-control analysis was conducted in a cohort of older adults being vaccinated with aTIV or naTIV/naQIV. Conditional logistic regression was adopted to estimate the odds ratio (OR) of all-cause hospitalizations occurred during the epidemic period.

Results

Of 58,252 patients vaccinated with aTIV and naTIV/naQIV for the first time, 2,504 cases of all-cause hospitalization (3.46 per 1,000 person-weeks) during the 18 influenza seasons were identified. Compared with naTIV/naQIV, aTIV was associated with a 12% reduced the odds of all-cause hospitalizations (OR 0.88; 95% CI: 0.80–0.97).

Conclusions

In an 18-season cohort of older adults, aTIV reduced the risk of all-cause hospitalizations when compared with naTIV/naQIV. Our findings confirm additional benefits for adjuvanted influenza vaccines in older adults.

KEYWORDS:

• Influenza vaccine
• older adults
• all-cause hospitalization
• primary care
• nested Case-Control studies

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/14760584.2022.2115362

Declaration of interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Francesco Lapi and Ettore Marconi provided consultancies in protocol preparation for epidemiological studies and data analyses for AstraZeneca, Pfizer, GSK, Seqirus and Sanofi Pasteur. Claudio Cricelli, Alessandro Rossi provided clinical consultancies for AstraZeneca, Pfizer, GSK, Seqirus and Sanofi Pasteur. Alexander Domnich was a permanent employee of Seqirus, a pharmaceutical company who manufacture and commercialize influenza vaccines.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Author contributions

All persons that contributed to this manuscript met the criteria for authorship and are listed as authors. Francesco Lapi, Alexander Domnich and Ettore Marconi were responsible for conceptualization, methodology, analysis, writing and editing of the manuscript. Alessandro Rossi and Claudio Cricelli were responsible for the critical review of the manuscript for important intellectual content. Francesco Lapi and Claudio Cricelli were responsible for validation of the manuscript.

Ethical standards:

Approval and informed consent The study protocol was approved by the Institutional Review Board (IRB) of the Italian College of General Practitioners and Primary Care. According to a by-law on the classification and implementation of observational drug-related research, as issued by the Italian National Drug Agency (an entity belonging to the Italian Ministry of Health), the present study does not require approval by an Ethics Committee in Italy (Italian Drug Agency note of 3 August 2007). This study followed the principles of the Declaration of Helsinki and compliant with the ENCePP (European Network of Centres for Pharmacoepidemiology and Pharmacovigilance) Guide on Methodological Standards in PharmacoepidemiologyThis study followed the principles of the Declaration of Helsinki and compliant with the ENCePP (European Network of Centres for Pharmacoepidemiology and Pharmacovigilance) Guide on Methodological Standards in Pharmacoepidemiology.

Additional information

Funding

This article was supported by theItalian College of General Practitioners and Primary Care. These findings havenot been presented elsewhere.