Effectiveness of Trivalent and Quadrivalent Inactivated Vaccines Against Influenza B in the United States, 2011-2012 to 2016-2017

A decade genetic diversity in Circulating influenza B virus in Iran (2010-2019): Divergence from WHO-recommended vaccine strains

BACKGROUND

Data on the disease burden and circulation patterns of influenza B virus lineages for Iran are limited.

OBJECTIVE

This review aims to describe the pattern of influenza B occurrence in Iran, comparing it with the proposed vaccine strains and determining the match and mismatch with the prescribed vaccine annually.

METHODS

Various sources were used to retrieve information of the data; such as information from an online search of databases such as FluNet, GISAID, and NCBI. After extracting protein sequence records in GISAID, sequence alignment with vaccine strain and construction of a phylogenetic tree were performed. Subsequently, categories of the registered circulating strains were evaluated for matching with the vaccine strains.

RESULTS

Of the total registered influenza-positive samples, 20.21% were related to influenza B virus. The phylogenic tree was designed based on 43 samples registered in the GISAID database; 76.74 and 23.25% sequences were of Yamagata and Victoria lineages, respectively. The most prevalent influenza B virus strains circulating during the study years belonged to the Yamagata lineage. In general, the match of the influenza B virus predominant circulating strains with administrated vaccines was observed in Iran. However, a high level of mismatch between the vaccine strain and Iranian isolates was identified in 2016‒2017.

CONCLUSION

The review of match and mismatch in influenza vaccine in order to improve the composition of the prescribed vaccine in each region is very important because the vaccine efficacy decreased when the strain included in vaccine did not match the circulating epidemic strain.

Immunogenicity and safety of the quadrivalent inactivated split-virion influenza vaccine in populations aged ≥ 3 years: A phase 3, randomized, double-blind, non-inferiority clinical trial

This study aimed to evaluate the immunogenicity non-inferiority and safety of the quadrivalent inactivated split-virion influenza vaccine in participants ≥ 3 years old. A total of 3,328 participants were enrolled. Participants 3-8 years old were administered one or two doses of the investigational vaccine or one dose of the control vaccine, whereas the other participants were administered only one dose of the investigational or control vaccine. The immunogenicity and occurrence of adverse events (AEs) after 30 days of full-course vaccination and serious adverse events (SAEs) within 6 months after full-course vaccination were assessed. The sero-conversion rates (SCRs) of anti-H1N1, H3N2, B(Y), and B(V) antibodies in the test group were 74.64%, 87.40%, 82.66%, and 78.89%, respectively, and their geometric mean titers were 1:250.13, 1:394.54, 1:200.84, and 1:94.91, respectively, which were non-inferior to those in the control group. The SCRs and sero-protection rates in the two-dose group of participants 3-8 years old were greater than those in the one-dose group. The incidences of total AEs and adverse reactions in the test group were 31.6% and 21.7%, respectively, which were close to those in the control group. In the two-dose group, the incidence of adverse reactions was considerably lower in the second dose (5.5%) than in the first dose (14.7%). Most AEs were grade 1 in severity, and no SAEs were recorded. The investigational vaccine had immunogenicity non-inferior to the control vaccine, and two doses were more effective than one dose in participants 3-8 years old, with a good overall safety.Trial registration: CTR20200715.

Urine Metabolome Dynamics Discriminate Influenza Vaccination Response

Influenza represents a major and ongoing public health hazard. Current collaborative efforts are aimed toward creating a universal flu vaccine with the goals of both improving responses to vaccination and increasing the breadth of protection against multiple strains and clades from a single vaccine. As an intermediate step toward these goals, the current work is focused on evaluating the systemic host response to vaccination in both normal and high-risk populations, such as the obese and geriatric populations, which have been linked to poor responses to vaccination. We therefore employed a metabolomics approach using a time-course (n = 5 time points) of the response to human vaccination against influenza from the time before vaccination (pre) to 90 days following vaccination. We analyzed the urinary profiles of a cohort of subjects (n = 179) designed to evenly sample across age, sex, BMI, and other demographic factors, stratifying their responses to vaccination as “High”, “Low”, or “None” based on the seroconversion measured by hemagglutination inhibition assay (HAI) from plasma samples at day 28 post-vaccination. Overall, we putatively identified 15,903 distinct, named, small-molecule structures (4473 at 10% FDR) among the 895 samples analyzed, with the aim of identifying metabolite correlates of the vaccine response, as well as prognostic and diagnostic markers from the periods before and after vaccination, respectively. Notably, we found that the metabolic profiles could unbiasedly separate the high-risk High-responders from the high-risk None-responders (obese/geriatric) within 3 days post-vaccination. The purine metabolites Guanine and Hypoxanthine were negatively associated with high seroconversion (p = 0.0032, p < 0.0001, respectively), while Acetyl-Leucine and 5-Aminovaleric acid were positively associated. Further changes in Cystine, Glutamic acid, Kynurenine and other metabolites implicated early oxidative stress (3 days) after vaccination as a hallmark of the High-responders. Ongoing efforts are aimed toward validating these putative markers using a ferret model of influenza infection, as well as an independent cohort of human seasonal vaccination and human challenge studies with live virus.

The role of cell-mediated immunity against influenza and its implications for vaccine evaluation

Influenza vaccines remain the most effective tools to prevent flu and its complications. Trivalent or quadrivalent inactivated influenza vaccines primarily elicit antibodies towards haemagglutinin and neuraminidase. These vaccines fail to induce high protective efficacy, in particular in older adults and immunocompromised individuals and require annual updates to keep up with evolving influenza strains (antigenic drift). Vaccine efficacy declines when there is a mismatch between its content and circulating strains. Current correlates of protection are merely based on serological parameters determined by haemagglutination inhibition or single radial haemolysis assays. However, there is ample evidence showing that these serological correlates of protection can both over- or underestimate the protective efficacy of influenza vaccines. Next-generation universal influenza vaccines that induce cross-reactive cellular immune responses (CD4+ and/or CD8+ T-cell responses) against conserved epitopes may overcome some of the shortcomings of the current inactivated vaccines by eliciting broader protection that lasts for several influenza seasons and potentially enhances pandemic preparedness. Assessment of cellular immune responses in clinical trials that evaluate the immunogenicity of these new generation vaccines is thus of utmost importance. Moreover, studies are needed to examine whether these cross-reactive cellular immune responses can be considered as new or complementary correlates of protection in the evaluation of traditional and next-generation influenza vaccines. An overview of the assays that can be applied to measure cell-mediated immune responses to influenza with their strengths and weaknesses is provided here.

Vaccine Effectiveness Against Influenza Hospitalization and Emergency Department Visits in 2 A(H3N2) Dominant Influenza Seasons Among Children <18 Years Old-New Vaccine Surveillance Network 2016-2017 and 2017-2018

Studies have shown egg-adaptive mutations in influenza vaccine strains that might have impaired protection against circulating A(H3N2) influenza viruses during the 2016-2017 and 2017-2018 seasons. We used the test-negative design and multivariable models to assess vaccine effectiveness against influenza-associated hospitalization and emergency department visits among children (<18 years old) during the 2016-2017 and 2017-2018 seasons. Effectiveness was 71% (95% confidence interval, 59%-79%), 46% (35%-55%), and 45% (33%-55%) against A(H1N1)pdm09, A(H3N2), and B viruses respectively, across both seasons. During high-severity seasons with concerns for vaccine mismatch, vaccination offered substantial protection against severe influenza outcomes requiring hospitalization or emergency department visits among children.

Development of virus-like particles-based vaccines against coronaviruses

Severe acute respiratory syndrome coronavirus (SARS‐CoV), Middle East respiratory syndrome coronavirus (MERS‐CoV), and the current severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) are the most impactful coronaviruses in human history, especially the latter, which brings revolutionary changes to human vaccinology. Due to its high infectivity, the virus spreads rapidly throughout the world and was declared a pandemic in March 2020. A vaccine would normally take more than 10 years to be developed. As such, there is no vaccine available for SARS‐CoV and MERS‐CoV. Currently, 10 vaccines have been approved for emergency use by World Health Organization (WHO) against SARS‐CoV‐2. Virus‐like particle (VLP)s are nanoparticles resembling the native virus but devoid of the viral genome. Due to their self‐adjuvanting properties, VLPs have been explored extensively for vaccine development. However, none of the approved vaccines against SARS‐CoV‐2 was based on VLP and only 4% of the vaccine candidates in clinical trials were based on VLPs. In the current review, we focused on discussing the major advances in the development of VLP‐based vaccine candidates against the SARS‐CoV, MERS‐CoV, and SARS‐CoV‐2, including those in clinical and pre‐clinical studies, to give a comprehensive overview of the VLP‐based vaccines against the coronaviruses.

Influenza vaccination and mortality among adults with heart failure in an integrated healthcare delivery system, 2009-2018

BACKGROUND

Influenza infection can result in decompensation or exacerbation of heart failure (HF) symptoms, hospitalization, and death.

OBJECTIVE

To examine the association of influenza vaccination with mortality and hospitalization during influenza and non-influenza seasons between 2009 and 2018.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective, observational cohort study, we included Kaiser Permanente Southern California members with a HF diagnosis prior to September 1 each year from 2009 to 2017.

EXPOSURE

The first influenza vaccination in each season (September 1 to May 31) was recorded. Vaccinated/unvaccinated patients were matched 1:1 on age, sex, and ejection fraction at the vaccination date (n-total = 74,870).

MAIN OUTCOMES

Patients were followed through the end of each influenza season for all-cause mortality. Secondary outcomes included cardiovascular mortality and all-cause hospitalization. In a sensitivity analysis, we examined mortality in the non-influenza season.

RESULTS

Influenza vaccinated vs unvaccinated patients had more comorbidities and higher healthcare utilization. After multivariable adjustment for utilization, sociodemographics, comorbidities, and medications, influenza vaccinated vs unvaccinated patients had a lower risk of all-cause mortality and cardiovascular mortality during the influenza season (hazard ratio [HR] 0.66, 95% confidence interval [CI] 0.63, 0.70 and HR 0.68, 95% CI 0.63, 0.74, respectively) but a higher risk of all-cause hospitalization (HR 1.27, 95% CI 1.21, 1.31). There was no association between influenza vaccination and all-cause or cardiovascular mortality during the non-influenza season (HR 0.99, 95% CI 0.89, 1.09 and HR 1.00, 95% CI 0.84, 1.21, respectively).

CONCLUSIONS

Influenza vaccination in HF patients was associated with a lower risk of mortality during the influenza season. Our findings provide support for recommendations of universal influenza vaccination in patients with HF.

Antigenic characterization of influenza and SARS-CoV-2 viruses

Antigenic characterization of emerging and re-emerging viruses is necessary for the prevention of and response to outbreaks, evaluation of infection mechanisms, understanding of virus evolution, and selection of strains for vaccine development. Primary analytic methods, including enzyme-linked immunosorbent/lectin assays, hemagglutination inhibition, neuraminidase inhibition, micro-neutralization assays, and antigenic cartography, have been widely used in the field of influenza research. These techniques have been improved upon over time for increased analytical capacity, and some have been mobilized for the rapid characterization of the SARS-CoV-2 virus as well as its variants, facilitating the development of highly effective vaccines within 1 year of the initially reported outbreak. While great strides have been made for evaluating the antigenic properties of these viruses, multiple challenges prevent efficient vaccine strain selection and accurate assessment. For influenza, these barriers include the requirement for a large virus quantity to perform the assays, more than what can typically be provided by the clinical samples alone, cell- or egg-adapted mutations that can cause antigenic mismatch between the vaccine strain and circulating viruses, and up to a 6-month duration of vaccine development after vaccine strain selection, which allows viruses to continue evolving with potential for antigenic drift and, thus, antigenic mismatch between the vaccine strain and the emerging epidemic strain. SARS-CoV-2 characterization has faced similar challenges with the additional barrier of the need for facilities with high biosafety levels due to its infectious nature. In this study, we review the primary analytic methods used for antigenic characterization of influenza and SARS-CoV-2 and discuss the barriers of these methods and current developments for addressing these challenges.

Lineage-matched versus mismatched influenza B vaccine effectiveness following seasons of marginal influenza B circulation

BACKGROUND

Several countries have recently transitioned from the trivalent inactivated influenza vaccine (TIV) to the quadrivalent inactivated influenza vaccine (QIV) in order to outweigh influenza B vaccine-mismatch. However, few studies thus far evaluated its benefits versus the TIV in a systematic manner. Our objective was to compare the QIV VE with lineage-mismatched TIV VE.

METHODS

We estimated the 2015-2016, 2017-2018, 2019-2020 end-of season influenza B VE against laboratory-confirmed influenza-like illness (ILI) among community patients, using the test-negative design. VE was estimated for pre-determined age groups and for moving age intervals of 15 years.

RESULTS

Since 2011-2012 season, alternate seasons in Israel were dominated by influenza B circulation. Compared with the lineage-mismatched TIV used during the 2015-2016 and 2017-2018 seasons, the 2019-2020 QIV showed the highest all-ages VE, with VE estimates of 56.9 (95% CI 30.1 to 73.4), 16.5 (95% CI -22.5 to 43.1) and -25.8 (95% CI -85.3 to 14.6) for the 2019-2020, 2017-2018 and 2015-2016 seasons, respectively. The 2019-2020 VE point estimated were the highest for the 0.5-4, 5-17 and 18-44 years age groups and for more 15-year age intervals as compared to the other seasons.

CONCLUSIONS

Our results support the rapid transition from the TIV to the QIV.

Effect of Antigenic Drift on Influenza Vaccine Effectiveness in the United States-2019-2020

BACKGROUND

At the start of the 2019-2020 influenza season, concern arose that circulating B/Victoria viruses of the globally emerging clade V1A.3 were antigenically drifted from the strain included in the vaccine. Intense B/Victoria activity was followed by circulation of genetically diverse A(H1N1)pdm09 viruses that were also antigenically drifted. We measured vaccine effectiveness (VE) in the United States against illness from these emerging viruses.

METHODS

We enrolled outpatients aged ≥6 months with acute respiratory illness at 5 sites. Respiratory specimens were tested for influenza by reverse-transcriptase polymerase chain reaction (RT-PCR). Using the test-negative design, we determined influenza VE by virus subtype/lineage and genetic subclades by comparing odds of vaccination in influenza cases versus test-negative controls.

RESULTS

Among 8845 enrollees, 2722 (31%) tested positive for influenza, including 1209 (44%) for B/Victoria and 1405 (51%) for A(H1N1)pdm09. Effectiveness against any influenza illness was 39% (95% confidence interval [CI]: 32-44), 45% (95% CI: 37-52) against B/Victoria and 30% (95% CI: 21-39) against A(H1N1)pdm09-associated illness. Vaccination offered no protection against A(H1N1)pdm09 viruses with antigenically drifted clade 6B.1A 183P-5A+156K HA genes (VE 7%; 95% CI: -14 to 23%) which predominated after January.

CONCLUSIONS

Vaccination provided protection against influenza illness, mainly due to infections from B/Victoria viruses. Vaccine protection against illness from A(H1N1)pdm09 was lower than historically observed effectiveness of 40%-60%, due to late-season vaccine mismatch following emergence of antigenically drifted viruses. The effect of drift on vaccine protection is not easy to predict and, even in drifted years, significant protection can be observed.

Synthetic vaccine affords full protection to mice against lethal challenge of influenza B virus of both genetic lineages

A quarter of all seasonal influenza cases are caused by type B influenza virus (IBV) that also dominates periodically. Here, we investigated a recombinant adenovirus vaccine carrying a synthetic HA2 representing the consensus sequence of all IBV hemagglutinins. The vaccine fully protected mice from lethal challenges by IBV of both genetic lineages, demonstrating its breadth of protection. The protection was not mediated by neutralizing antibodies but robust antibody-dependent cellular cytotoxicity and cell-mediated immune responses. Complete protection of the animals required the entire codon-optimized HA2 sequence that elicited a balanced immune response, whereas truncated vaccines without either the fusion peptide or the transmembrane domain reduced the efficacy of protection. Finally, the vaccines did not demonstrate any sign of disease exacerbation following lung pathology and morbidity monitoring. Collectively, these data suggest that it could be worth further exploring this prototype universal vaccine because of its considerable efficacy, safety, and breadth of protection.

Mosaic Hemagglutinin-Based Whole Inactivated Virus Vaccines Induce Broad Protection Against Influenza B Virus Challenge in Mice

Influenza viruses undergo antigenic changes in the immuno-dominant hemagglutinin (HA) head domain, necessitating annual re-formulation of and re-vaccination with seasonal influenza virus vaccines for continuing protection. We previously synthesized mosaic HA (mHA) proteins of influenza B viruses which redirect the immune response towards the immuno-subdominant conserved epitopes of the HA via sequential immunization. As ~90% of current influenza virus vaccines are manufactured using the inactivated virus platform, we generated and sequentially vaccinated mice with inactivated influenza B viruses displaying either the homologous (same B HA backbones) or the heterologous (different B HA backbones) mosaic HAs. Both approaches induced long-lasting and cross-protective antibody responses showing strong antibody-dependent cellular cytotoxicity (ADCC) activity. We believe the B virus mHA vaccine candidates represent a major step towards a universal influenza B virus vaccine.

Lineage-specific protection and immune imprinting shape the age distributions of influenza B cases

How a history of influenza virus infections contributes to protection is not fully understood, but such protection might explain the contrasting age distributions of cases of the two lineages of influenza B, B/Victoria and B/Yamagata. Fitting a statistical model to those distributions using surveillance data from New Zealand, we found they could be explained by historical changes in lineage frequencies combined with cross-protection between strains of the same lineage. We found additional protection against B/Yamagata in people for whom it was their first influenza B infection, similar to the immune imprinting observed in influenza A. While the data were not informative about B/Victoria imprinting, B/Yamagata imprinting could explain the fewer B/Yamagata than B/Victoria cases in cohorts born in the 1990s and the bimodal age distribution of B/Yamagata cases. Longitudinal studies can test if these forms of protection inferred from historical data extend to more recent strains and other populations.

Influenza B viruses: underestimated and overlooked

Influenza B viruses circulate globally every year causing respiratory disease with significant clinical and socio-economic impacts. IBV are considered exclusive human pathogens with no established animal reservoirs, which suggests with concerted effort it may be possible to eradicate this virus from human circulation. However, this requires a deeper understanding of IBV virology and immunology and the design of vaccines that induce universal immunity to antigenic variants of IBV.

Natural immunity to influenza A and B among Saudi blood donors in Al Madinah Al Munawarah, Saudi Arabia

Objectives:

To investigate the seroprevalence of influenza viruses (A and B) among blood donors in Kingdom of Saudi Arabia.

Methods:

The present investigation was conducted between April 2019 and July 2019. Participants were healthy adults recruited from the central blood bank Al Madinah Al Munawarah, Kingdom of Saudi Arabia. Immunoglobulin G (IgG) levels against influenza A and B were measured in serum samples using ELISA.

Results:

The results showed that 29.2% of the sample had significant concentrations of influenza A IgG antibody, whereas 38.6% had significant concentrations of influenza B IgG antibody. A strong correlation was found between the levels of influenza A and influenza B antibodies (r=0.708, p<0.001). The number of individuals identified as negative for influenza A IgG antibody increased with age (p<0.01). In addition, no correlations were identified between influenza A IgG and influenza B IgG and body mass index (BMI), (p>0.05). Finally, linear regression analysis showed that the level of influenza A antibody can be predicted by age (p<0.05) and body mass index (BMI) (p<0.05).

Conclusion:

Approximately one-third of Saudi Arabian adults presented significant levels of influenza A and B antibodies in our study. Demographic factors, including age and BMI, might contribute to influenza A antibody levels.

Influenza vaccine effectiveness against laboratory-confirmed influenza in a vaccine-mismatched influenza B-dominant season

BACKGROUND

The 2017-2018 influenza season in Israel was characterized by the predominance of influenza B Yamagata, with a lesser circulation of influenza A(H1N1)pdm09 and influenza A(H3N2). We estimated vaccine effectiveness (VE) of the inactivated influenza vaccine which was selected for use that season.

METHODS

End-of-season VE and 95% confidence intervals (CI) against laboratory-confirmed influenza-like illness (ILI) were estimated by means of the test-negative design. Age-specific VE analysis was carried out using a moving age interval.

RESULTS

Specimen were obtained from 1,453 community ILI patients; 610 (42.0%) were influenza-positive, among which 69.7% were B, 17.2% A(H1N1)pdm09 and 13.4% A(H3N2). A 98.6% of molecularly characterized influenza B belonged to the Yamagata lineage. Of the sampled individuals, 1320 were suitable for VE analysis. Of those vaccinated, 90.6% received the inactivated trivalent influenza vaccine (TIV) containing a Victoria lineage influenza B-like virus. VE against influenza A differed by age, with the highest VE of 72.9% (95%CI 31.9-89.2%) observed in children 0.5-14 years old, while all ages VE was 46.6% (95%CI 10.4-68.2%). All ages VE against influenza B was 23.2% (95%CI -10.1-46.4%) with age-specific analysis showing non-significant VE estimates. Utilizing a moving age interval of 15 years, afforded a detailed age-specific insight into influenza VE against the influenza viruses circulating during the 2017-2018 season.

CONCLUSIONS

The moderate-high 2017-2018 influenza A VE among children and adolescents, supports seasonal influenza vaccination at a young age. The low VE against influenza B in Israel, is most likely the result of influenza B/TIV-mismatch.

Interim estimates of 2019/20 vaccine effectiveness during early-season co-circulation of influenza A and B viruses, Canada, February 2020

Interim results from Canada's Sentinel Practitioner Surveillance Network show that during a season characterised by early co-circulation of influenza A and B viruses, the 2019/20 influenza vaccine has provided substantial protection against medically-attended influenza illness. Adjusted VE overall was 58% (95% confidence interval (CI): 47 to 66): 44% (95% CI: 26 to 58) for A(H1N1)pdm09, 62% (95% CI: 37 to 77) for A(H3N2) and 69% (95% CI: 57 to 77) for influenza B viruses, predominantly B/Victoria lineage.

La gripe: 76 años de vacuna antigripal… ¡y de la hemaglutinina!

Se revisa someramente la historia de los virus gripales y los pasos dados desde que se utilizó masivamente la primera vacuna de virus completos, hasta la descripción de las distintas vías de vehiculizar o de administrar la hemaglutinina de las que disponemos en la actualidad, en aras de mejorar la respuesta inmune y por tanto la protección clínica de toda la población. Se exponen brevemente los requisitos que debería cumplir una futura vacuna “universal” para que pudiera ser usada con carácter sistemático y los distintos proyectos en marcha.