Significant circulation of influenza B viruses mismatching the recommended vaccine-lineage in South Korea, 2007-2014

Impact of sex on humoral immunity with live influenza B virus vaccines in mice

Influenza B virus (FLUBV) poses a significant infectious threat, with frequent vaccine mismatch limiting its effectiveness. Our previous work investigated the safety and efficacy of modified live attenuated FLUBV vaccines with rearranged genomes (FluB-RAM and FluB-RANS) or a temperature-sensitive PB1 segment with a C-terminal HA tag (FluB-att). In this study, we compared the immune responses of female and male DBA/2J mice vaccinated with these vaccines, including versions containing a chimeric HA segment with an N-terminal IgA-inducing peptide (IGIP). Importantly, both recombinant viruses with and without IGIP remained genetically stable during egg passage. We found that introducing IGIP strengthened vaccine attenuation, particularly for FluB-RAM/IGIP. Prime-boost vaccination completely protected mice against lethal challenge with a homologous FLUBV strain. Notably, recombinant viruses induced robust neutralizing antibody responses (hemagglutination inhibition titers ≥40) alongside antibodies against NA and NP. Interestingly, female mice displayed a consistent trend of enhanced humoral and cross-reactive IgG and IgA responses against HA, NA, and NP compared to male counterparts, regardless of the vaccine used. However, the presence of IGIP generally led to lower anti-HA responses but higher anti-NA and anti-NP responses, particularly of the IgA isotype. These trends were further reflected in mucosal and serological responses two weeks after challenge, with clear distinctions based on sex, vaccine backbone, and IGIP inclusion. These findings hold significant promise for advancing the development of universal influenza vaccines.

Increasing serum antibodies against type B influenza virus in 2017-2018 winter in Beijing, China

Influenza B virus circulates yearly with lower activity than that of influenza A virus in China. During winter 2017 to 2018, a sharp surge of influenza activity dominated by type B/Yamagata lineage virus caused unprecedented medical burden in Beijing. This research aimed to understand the underlying mechanism for this circulation and prepare for epidemics in the future. Sera samples collected from the patients in 2016–2017 and 2017–2018 flu seasons were tested for profiling hemagglutinin inhibition (HI) antibodies against both prevailing Victoria and Yamagata lineages of type B influenza viruses. It showed that the seroprevalence against both lineages of the virus in 2017–2018 winter was higher than that in 2016–2017, while no difference of the seroprevalence was observed between the two viruses. Meanwhile, significant elevated geometric mean titer (GMT) against both lineages of influenza B viruses was found in the specimens collected during 2017–2018 flu season than that from 2016 to 2017, suggesting the viruses might undergo antigenic changes. These results also suggested that lower GMT against both type B variants in 2016–2017 might serve as an immunological niche for the dominating of B/Yamagata virus in China during 2017–2018 winter season. Our findings have implication that there was a significantly elevation of HI antibodies to influenza viruses B in 2017–2018 than in 2016–2017. On the other hand, the low level of HI antibodies to both B/Y and B/V in 2016–2017 could contribute to the severe B/Y epidemic in 2017–2018 to some extent.

Cost-effectiveness analysis of quadrivalent seasonal influenza vaccines in Beijing: A modeling analysis

BACKGROUND

Since 2007, Beijing has offered a free trivalent influenza vaccine (TIV) for residents aged ≥ 60 years and school students. The quadrivalent influenza vaccine (QIV) was administered to school children in 2018 and will be administered to elderly adults in the future. In addition, health care workers (HCWs) who are involved in the prevention and control of COVID-19 were included in the program in 2020. This study aimed to analyze the cost-effectiveness of a comprehensive list of combined strategies of TIV and QIV for school children, elderly adults, and HCWs to identify the most cost-effective strategy.

METHODS

A decision tree was developed to compare 1-year outcomes of TIV vs. QIV in three risk groups: school children, elderly adults, and HCWs. The outcome was incremental cost per quality-adjusted life-year (QALY). Probabilistic sensitivity analyses and scenario analyses were developed to assess the robustness of the results.

RESULTS

From the perspective of society, this study found that the introduction of QIVs can be cost-effective for any and all targeted groups with a willingness-to-pay threshold of 3-fold GDP per capita. Among all programs, program H (all school children, elderly adults, and HCWs received the QIV) showed a 79% probability of being cost-effective with an incremental cost-effectiveness ratio (ICER) of 13,580 (95% CI: 13,294, 13,867) US$/QALY and was the preferred option in the base case scenario.

CONCLUSION

The introduction of QIVs to school children, elderly adults, or HCWs is likely to be cost-effective, either separately or collectively. The introduction of QIV to school children, elderly adults, and health care workers simultaneously showed the highest probability of being cost-effective and was the preferred option.

FluB-RAM and FluB-RANS: Genome Rearrangement as Safe and Efficacious Live Attenuated Influenza B Virus Vaccines

Influenza B virus (IBV) is considered a major respiratory pathogen responsible for seasonal respiratory disease in humans, particularly severe in children and the elderly. Seasonal influenza vaccination is considered the most efficient strategy to prevent and control IBV infections. Live attenuated influenza virus vaccines (LAIVs) are thought to induce both humoral and cellular immune responses by mimicking a natural infection, but their effectiveness has recently come into question. Thus, the opportunity exists to find alternative approaches to improve overall influenza vaccine effectiveness. Two alternative IBV backbones were developed with rearranged genomes, rearranged M (FluB-RAM) and a rearranged NS (FluB-RANS). Both rearranged viruses showed temperature sensitivity in vitro compared with the WT type B/Bris strain, were genetically stable over multiple passages in embryonated chicken eggs and were attenuated in vivo in mice. In a prime-boost regime in naïve mice, both rearranged viruses induced antibodies against HA with hemagglutination inhibition titers considered of protective value. In addition, antibodies against NA and NP were readily detected with potential protective value. Upon lethal IBV challenge, mice previously vaccinated with either FluB-RAM or FluB-RANS were completely protected against clinical disease and mortality. In conclusion, genome re-arrangement renders efficacious LAIV candidates to protect mice against IBV.

Reverse genetics for influenza B viruses and recent advances in vaccine development

Influenza B virus is a respiratory pathogen that affects more severely the pediatric and elderly populations. There are two lineages of influenza B virus that seem to have differential predilection for age groups. Both lineages can co-circulate during the influenza season however one is usually more prominent than the other depending on the season. There are no defined indicators to predict which lineage will dominate in any given season. In recent years, the addition of viruses from both lineages to the seasonal influenza vaccine formulation has improved vaccine protection, although quadrivalent vaccines are not available worldwide. Reverse genetics has facilitated advancements in the field of vaccine development against influenza B virus. Different strategies have been explored showing promising results that could potentially lead to the development broadly protective influenza B virus vaccines.

Clinical similarities between influenza A and B in children: a single-center study, 2017/18 season, Korea

Background

The global burden of seasonal influenza on medical care has been one of the greatest in the pediatric population. The attention drawn to influenza B was relatively low compared to influenza A, probably because the influenza B virus was thought to be less virulent and have a lower pandemic potential. This study aimed to compare the clinical features of influenza A and B in children.

Methods

This retrospective study included children diagnosed and treated for influenza as inpatients or outpatients during the 2017/18 influenza season at a tertiary referral hospital. Data regarding clinical characteristics, diagnoses, laboratory results, and vaccination histories were collected and reviewed.

Results

Over the study period, 128 patients with influenza A and 109 patients with influenza B were identified. The mean age of patients with influenza B was significantly higher than that of patients with influenza A (5.6 ± 4.4 vs 4.1 ± 4.4 years, p = 0.010). Fever was the most common manifestation of influenza followed by respiratory symptoms. No single symptom was specifically associated with either type of influenza. The total duration of fever (4.3 ± 2.3 vs 3.7 ± 2.6 days), ‘time from fever onset to initiation of antivirals’, and ‘time from initiation of antivirals to defervescence’ were similar between the two influenza types, even though all three time periods tended to be longer for influenza B. The platelet counts and proportions of neutrophils were higher for influenza A than for influenza B infections, although the values were within normal limits for both influenza types.

Conclusions

We found overall clinical similarities between influenza A and B with no less clinical significance or severity of influenza B compared to those of influenza A. Equal levels of awareness and attention should be paid to both influenza types.

Randomized, single-blind, active-controlled phase I clinical trial to evaluate the immunogenicity and safety of GC3114 (high-dose, quadrivalent influenza vaccine) in healthy adults

Influenza is a major medically attended respiratory illness. The impact of influenza on morbidity and mortality is particularly high in the elderly. Immunosenescence attenuates the immune response of influenza vaccine in the elderly. High-dose influenza vaccine contains 60 μg of hemagglutinin per strain, four times more compared with standard-dose (SD) influenza vaccine. This study is a phase I clinical trial investigating the immunogenicity and safety of the GC3114, high-dose, quadrivalent inactivated influenza vaccine (HD-QIV) in healthy adults aged 19-64 years during the 2017-2018 season. Seroprotection rates of HD-QIV were 100.0% for A/H1N1, 96.67% for A/H3N2, 83.33% for B/Yamagata, and 96.67% for B/Victoria. Seroconversion rate for A/H1N1, A/H3N2, B/Yamagata, and B/Victoria strains were 86.67%, 90.0%, 53.33%, and 53.33%, respectively, in the HD-QIV group. The post-/pre-vaccination geometric mean titer ratio (GMTR) was 15.28 for A/H1N1, 8.19 for A/H3N2, 3.56 for B/Yamagata, and 3.03 for B/Victoria in the HD-QIV group. Seroconversion rate and post-/pre-vaccination GMTR for A/H3N2 were significantly higher in the HD-QIV group than in the SD-QIV group (control). No serious adverse events were reported. In conclusion, GC3114 was safe, well-tolerated, and immunogenic in healthy adults. Clinical Trials Identifier: NCT03357263.

Association of Consecutive Influenza Vaccinations and Pneumonia: A Population-Based Case-Control Study

The purpose of this study was to investigate whether individuals receiving influenza vaccines have a lower risk of pneumonia. A nationwide population-based case-control study was conducted using data from the National Health Insurance Research Database in Taiwan. We enrolled 7565 patients each in pneumonia and non-pneumonia groups after diagnosis of patients with chronic pulmonary disease, and these patients were individually age and sex matched in a 1:1 ratio. Using conditional logistic regression analysis, adjusted odds ratios (aORs) were estimated in patients who received influenza vaccination and those who had not previously had pneumonia. Moreover, we also analyzed the interval between vaccination and the onset of pneumonia and the number of vaccinations received by patients. This was compared with patients who never received influenza vaccination. Patients who had received influenza vaccination and had been vaccinated for two consecutive years (aOR = 0.85, confidence interval (CI) = 0.79–0.93 and aOR = 0.75, CI = 0.67–0.85, respectively) showed lower rates of pneumonia occurrence by 15–25%. In conclusion, influenza vaccination significantly reduces the occurrence of pneumonia, especially in individuals who receive vaccination in consecutive years.