Summary of the NACI literature review on the comparative effectiveness of subunit and split virus inactivated influenza vaccines in older adults

Influenza Vaccine Type-Dependent Antibody Response in Patients with Autoimmune Inflammatory Rheumatic Diseases

BACKGROUND

The study aimed to explore influenza antibody response in patients with autoimmune inflammatory rheumatoid diseases (AIIRDs) stratified by the different vaccine types applied in Denmark during the 2018-2019 influenza season.

METHODS

Included patients were diagnosed with rheumatoid arthritis, psoriatic arthritis, or spondyloarthritis receiving biological disease-modifying antirheumatic drugs (bDMARDs) with or without conventional synthetic disease-modifying antirheumatic drugs. Influenza vaccination status in the 2018-2019 season and vaccine type received were reviewed in the Denmark. Blood samples were drawn ≥ 14 days post vaccination, and antibody titers were determined by the hemagglutinin inhibition (HAI) assay for the serotypes A/Michigan/H1N1, A/Singapore/H3N2, and B/Colorado included in the influenza vaccines in the 2018-2019 season. An overall serotype HAI geometric mean titer (GMT) was calculated from the 3 serotype-specific HAI titers. An overall serotype HAI GMT ≥ 40 was considered protective.

RESULTS

Of the 205 included patients, 105 (51%) had received influenza vaccination. One-quarter of vaccinated patients achieved post-vaccination overall serotype HAI GMT ≥40. For patients vaccinated with Influvac, a significantly higher proportion had HAI titers ≥ 40 for 2 serotypes, namely, A/Michigan/H1N1 and A/Singapore/H3N2, than patients vaccinated with Vaxigrip or VaxigripTetra. The same applied to all serotypes HAI GMT, where significantly more patients who received Influvac achieved postvaccination HAI GMT≥40 versus patients who received Vaxigrip (p=0.02) or VaxigripTetra (p=0.002). The latter outcome was explored in a multivariable logistic regression analysis and remained significant when including the following variables: age, sex, treatment with methotrexate and/or prednisolone, type of influenza vaccine, time interval from vaccination to antibody measurement, and previous vaccination status.

CONCLUSION

Influenza antibody levels following vaccination with Influvac in bDMARD-treated patients with AIIRDs were superior to Vaxigrip and VaxigripTetra. Treatment with methotrexate (MTX) did not reduce the antibody response.

Immunogenicity of H5N1 influenza vaccines in elderly adults: a systematic review and meta-analysis

Several different vaccines have been produced for human use to prevent the highly pathogenic H5N1 influenza. Some studies reported that the clinical effectiveness of influenza vaccines in older adults may be lower than in younger adults. In this study, a meta-analysis of the immunogenicity of H5N1 influenza vaccines in elderly adults was performed. Database search was conducted in EMBASE, PubMed, the Cochrane Library, Chinese VIP, Wanfang and CBM. A total of 3951 elderly adults from 10 articles were included in the meta-analysis. Compared to a single dose, two doses of H5N1 vaccines resulted in the higher seroconversion and seroprotection. For all groups treated with adjuvanted vaccines, there were significant increases (1.55- to 2.16-fold) in the seroconversion rates (SCRs) and seroprotection rates (SPRs) after two immunizations. Oil-in-water emulsion (OE)-adjuvanted 7.5 μg vaccine caused higher antibody responses than 3.75 μg of vaccine (SCR: risk ratio (RR) = 1.26 (1.19, 1.33); SPR: RR = 1.25 (1.14, 1.36)). Elderly adults exhibited slightly lower antibody responses only when given 7.5 μg of OE-adjuvanted vaccine (SCR: RR = 1.06 (1.01, 1.11)) than younger adults. After treatment with the 7.5 μg of OE-adjuvanted vaccines, the most commonly reported adverse events were injection site pain, swelling and erythema, with the incidence of 32%, 3% and 2%, respectively, and no serious adverse events were found. These data demonstrate that two doses of 7.5 µg of OE-adjuvanted H5N1 vaccine are well tolerated and induce a robust antibody response in elderly adults.