MF59-adjuvanted and virosomal influenza vaccines for preventing influenza hospitalization in older people: comparative effectiveness using the Valencia health care information system.

BACKGROUND

Adjuvanted influenza vaccines offer greater and broader immunogenicity to older adults than conventional vaccines. Studies assessing the comparative effectiveness of adjuvanted influenza vaccines in this age group are lacking.

METHODS

We conducted a retrospective cohort study to estimate the comparative effectiveness of MF59-adjuvanted trivalent influenza vaccine (TIV) and virosomal-TIV for prevention of influenza hospitalization in adults aged ≥65 years. We obtained administrative data on immunization status and influenza hospitalization for the 2010-2011 influenza season. We used Cox regression models to assess comparative effectiveness; crude and adjusted by age, sex, comorbidity, deprivation, type of insurance, and travel time to hospital. We accounted for data clustering at the hospital level by using a multilevel random effects model.

RESULTS

Overall, 373,798 vaccinated subjects were evaluated. There were 40 hospitalizations for influenza among 176,618 subjects, contributing 4,288,109 person-weeks at risk in the virosomal-TIV group, and 37 hospitalizations for influenza among 197,180 subjects, contributing 4,786,360 person-weeks at risk in the MF59-TIV group. The crude hazard ratio (HR) was 0.83 (0.53-1.30), and the adjusted Cox estimated HR of MF59-TIV relative to virosomal-TIV was 0.86 (0.55-1.35). After accounting for data clustering, the HR of influenza hospitalization associated with MF59-TIV relative to virosomal-TIV was 0.94 (0.37-2.38).

CONCLUSION

During the 2010-2011 influenza season, we found no differences in the risk of influenza hospitalization in subjects aged ≥65 years vaccinated with MF59-TIV compared with those vaccinated with virosomal-TIV.