Long-term outcome of the humoral and cellular immune response of an H5N1 adjuvanted influenza vaccine in elderly persons: 2-year follow-up of a randomised open-label study

Vaccine strain affects seroconversion after influenza vaccination in COPD patients and healthy older people

Though clinical guidelines recommend influenza vaccination for chronic obstructive pulmonary disease (COPD) patients and other high-risk populations, it is unclear whether current vaccination strategies induce optimal antibody responses. This study aimed to identify key variables associated with strain-specific antibody responses in COPD patients and healthy older people. 76 COPD and 72 healthy participants were recruited from two Australian centres and inoculated with influenza vaccine. Serum strain-specific antibody titres were measured pre- and post-inoculation. Seroconversion rate was the primary endpoint. Antibody responses varied between vaccine strains. The highest rates of seroconversion were seen with novel strains (36-55%), with lesser responses to strains included in the vaccine in more than one consecutive year (27-33%). Vaccine responses were similar in COPD patients and healthy participants. Vaccine strain, hypertension and latitude were independent predictors of seroconversion. Our findings reassure that influenza vaccination is equally immunogenic in COPD patients and healthy older people; however, there is room for improvement. There may be a need to personalise the yearly influenza vaccine, including consideration of pre-existing antibody titres, in order to target gaps in individual antibody repertoires and improve protection.

Persistence of vaccine-induced antibody to A/H5N1 influenza after 30 and 36 months of vaccination

Objectives

An A/H5N1 vaccine named IVACFLU-A/ H5N1 was accepted to use in Vietnam, however, antibody persistence after vaccination has not been well characterized yet. We examined the persistence of antibodies after vaccination and related risk factors in individuals enrolled in phase II with 15 mcg dose, 2 injections 21 days apart, IVACFLU-A/ H5N1 vaccine trials in Ninh Hoa, Vietnam.

Methods

We used a longitudinal study to follow 86 participants without control groups. They were tested anti-A/H5N1 IgG seronegative at baseline and received all two doses of the vaccine. Blood was drawn at 30 and 36 months after the full vaccination to assess antibody status. Antibody persistence status is compared by demographics and exposure risk factors using a univariate logistic regression.

Results

Overall incidence of persisting at least 1/10 of A/H5N1 antibodies was 84.9% and 52.3% after 30 months and 36 months of IVACFLU-A/H5N1 vaccination. The odds of antibody persistence were more significant in older people but lower in people who experienced flu-like symptoms in the past 18 months or between two visits. We recorded no differences between A/H5N1 antibodies persistence and exposure risk factors including having poultry farms, contacting with poultry, and slaughtering and processing poultry.

Conclusion

This study demonstrated noteworthy antibody persistence, indicated by seroconversion rate and geometric mean titer at 30 and 36-month post-vaccination, of the IVACFLU-A/H5N1 vaccine. There is a need for further studies on older people, and those who experienced flu-like symptoms to decide the suitable time for the booster shot.

Antibody avidity, persistence, and response to antigen recall: comparison of vaccine adjuvants

Differences in innate immune ‘imprinting’ between vaccine adjuvants may mediate dissimilar effects on the quantity/quality of persisting adaptive responses. We compared antibody avidity maturation, antibody/memory B cell/CD4⁺ T cell response durability, and recall responses to non-adjuvanted fractional-dose antigen administered 1-year post-immunization (Day [D]360), between hepatitis B vaccines containing Adjuvant System (AS)01_B, AS01_E, AS03, AS04, or Alum (NCT00805389). Both the antibody and B cell levels ranked similarly (AS01_B/E/AS03 > AS04 > Alum) at peak response, at D360, and following their increases post-antigen recall (D390). Proportions of high-avidity antibodies increased post-dose 2 across all groups and persisted at D360, but avidity maturation appeared to be more strongly promoted by AS vs. Alum. Post-antigen recall, frequencies of subjects with high-avidity antibodies increased only markedly in the AS groups. Among the AS, total antibody responses were lowest for AS04. However, proportions of high-avidity antibodies were similar between groups, suggesting that MPL in AS04 contributes to avidity maturation. Specific combinations of immunoenhancers in the AS, regardless of their individual nature, increase antibody persistence and avidity maturation.

A systematic review and meta-analysis on the safety of newly adjuvanted vaccines among older adults

INTRODUCTION

New adjuvants have been developed to improve the efficacy of vaccines and for dose-sparing capacity and may overcome immuno senescence in the elderly. We reviewed the safety of newly-adjuvanted vaccines in older adults.

METHODS

We searched Medline for clinical trials (CTs) including new adjuvant systems (AS01, AS02, AS03, or MF59), used in older adults, published between 01/1995 and 09/2017. Safety outcomes were: serious adverse events (SAEs); solicited local and general AEs (reactogenicity); unsolicited AEs; and potentially immune-mediated diseases (pIMDs). Standard random effects meta-analyses were conducted by type of safety event and adjuvant type, reporting Relative Risks (RR) with 95% confidence intervals (95% CI).

RESULTS

We identified 1040 publications, from which we selected 7, 7, and 12 CTs on AS01/AS02, AS03 and MF59, respectively. 47,602 study participants received newly-adjuvanted vaccine and 44,521 control vaccine, or placebo. Rates of SAEs (RR = 0.99, 95% CI = 0.96-1.02), deaths (RR = 0.99, 95% CI = 0.92-1.06) and pIMDs (RR = 0.94, 95% CI = 0.79-1.1) were comparable in newly-adjuvanted and control groups. Vaccine-related SAEs occurred in <1% of the subjects in both groups. The reactogenicity of AS01/AS02 and AS03 adjuvanted vaccines was higher compared to control vaccines, whereas MF59-adjuvanted vaccines resulted only in more pain. Grade 3 reactogenicity was reported infrequently, with fatigue (RR = 2.48, 95% CI = 1.69-3.64), headache (RR = 2.94, 95% CI = 1.24-6.95), and myalgia (RR = 2.68, 95% CI = 1.86-3.80) occurring more frequently in newly-adjuvanted groups. Unsolicited AEs occurred slightly more frequently in newly-adjuvanted groups (RR = 1.04, 95% CI = 1.00-1.08).

CONCLUSIONS

Our review suggests that, within the clinical trial setting, the use of new adjuvants in older adults has not led to any safety concerns, with no increase in SAEs or fatalities. Higher rates for solicited AEs were observed, especially for AS01/AS02 and AS03 adjuvanted vaccines, but AEs were mostly mild and transient. Further evidence will need to come from the use of new adjuvants in the real-world setting, where larger numbers can be studied to potentially detect rare reactions.

Influenza immunology evaluation and correlates of protection: a focus on vaccines

Vaccination is the most effective method of controlling seasonal influenza infections and preventing possible pandemic events. Although influenza vaccines have been licensed and used for decades, the potential correlates of protection induced by these vaccines are still a matter of discussion. Currently, inactivated vaccines are the most common and the haemagglutination inhibition antibody titer is regarded as an immunological correlate of protection and the best available parameter for predicting protection from influenza infection. However, the assay shows some limitations, such as its low sensitivity to B and avian strains and inter-laboratory variability. Additional assays and next-generation vaccines have been evaluated to overcome the limitations of the traditional serological techniques and to elicit broad immune responses, underlining the need to revise the current correlates of protection. The aim of this review is to provide an overview of the current scenario regarding the immunological evaluation and correlates of protection of influenza vaccines.