Influenza-like Illness Incidence Is Not Reduced by Influenza Vaccination in a Cohort of Older Adults, Despite Effectively Reducing Laboratory-Confirmed Influenza Virus Infections

Measuring the impact of influenza vaccination in the Netherlands using retrospective observational primary care, hospitalisation and mortality data

We aimed to estimate the impact of influenza vaccination in the Netherlands using general practitioner medical records for 2011-2020. We found that vaccinees had higher consultation rates for influenza-like-illness, acute respiratory infections, and pneumonia, as well as antibiotic use, hospitalisations, and several control diagnoses (i.e. illnesses for which there was no a priori expectation that influenza vaccination would play a protective effect). We found similar rates for respiratory mortality and lower all-cause mortality in the vaccinees versus non-vaccinees, mainly driven by the 75+ age group. These results expand, but are fairly consistent with those of previous investigations, and highlight the difficulty of using registry data to assess the impact of vaccination, because of underlying differences between vaccinees and non-vaccinees. Whether these biases also play a role for hospitalisations and mortality remains unclear. Our findings support the implementation of randomized studies to assess the impact of influenza vaccination.

Multiple vaccine comparison in the same adults reveals vaccine-specific and age-related humoral response patterns: an open phase IV trial

Vaccine responsiveness is often reduced in older adults. Yet, our lack of understanding of low vaccine responsiveness hampers the development of effective vaccination strategies to reduce the impact of infectious diseases in the ageing population. Young-adult (25-49 y), middle-aged (50-64 y) and older-adult ( ≥ 65 y) participants of the VITAL clinical trials (n = 315, age-range: 28-98 y), were vaccinated with an annual (2019-2020) quadrivalent influenza (QIV) booster vaccine, followed by a primary 13-valent pneumococcal-conjugate (PCV13) vaccine (summer/autumn 2020) and a primary series of two SARS-CoV-2 mRNA-1273 vaccines (spring 2021). This unique setup allowed investigation of humoral responsiveness towards multiple vaccines within the same individuals over the adult age-range. Booster QIV vaccination induced comparable H3N2 hemagglutination inhibition (HI) titers in all age groups, whereas primary PCV13 and mRNA-1273 vaccination induced lower antibody concentrations in older as compared to younger adults (primary endpoint). The persistence of humoral responses, towards the 6 months timepoint, was shorter in older adults for all vaccines (secondary endpoint). Interestingly, highly variable vaccine responder profiles overarching multiple vaccines were observed. Yet, approximately 10% of participants, mainly comprising of older male adults, were classified as low responders to multiple vaccines. This study aids the identification of risk groups for low vaccine responsiveness and hence supports targeted vaccination strategies. Trial number: NL69701.041.19, EudraCT: 2019-000836-24.

Quantity and Quality of Naturally Acquired Antibody Immunity to the Pneumococcal Proteome Throughout Life

BACKGROUND

Young children and older adults are susceptible for invasive pneumococcal disease (IPD) caused by Streptococcus pneumoniae. Pneumococcal protein-specific antibodies play a protective role against IPD; however, not much is known about the pace of acquisition, maturation, and maintenance of these antibodies throughout life.

METHODS

Immunoglobulin G (IgG) and IgA levels, avidity, and/or specificity to the pneumococcal proteome in serum and saliva from healthy young children, adults, and older adults, with known carriage status, were measured by enzyme-linked immunosorbent assay (ELISA) and 2-dimensional western blotting against ΔcpsTIGR4.

RESULTS

Eleven-month-old children, the youngest age group tested, had the lowest pneumococcal proteome-specific IgG and IgA levels and avidity in serum and saliva, followed by 24-month-old children and were further elevated in adult groups. Among adult groups, the parents had the highest serum and saliva IgG and IgA antibody levels. In children, antibody levels and avidity correlated with daycare attendance and presence of siblings, posing as proxy for exposure and immunization. Immunodominance patterns slightly varied throughout life.

CONCLUSIONS

Humoral immunity against the pneumococcal proteome is acquired through multiple episodes of pneumococcal exposure. Low-level and low-avidity antiproteome antibody profiles in young children may contribute to their IPD susceptibility, while in overall antiproteome antibody-proficient older adults other factors likely play a role.

Prevalence of human respiratory pathogens and associated mucosal cytokine levels in young children and adults: a cross-sectional observational study in the Netherlands during the winter of 2012/2013

Respiratory pathogens can cause severe disease and even death, especially in the very young and very old. Studies investigating their prevalence often focus on individuals presenting to healthcare providers with symptoms. However, the design of prevention strategies, e.g. which target groups to vaccinate, will benefit from knowledge on the prevalence of, risk factors for and host response to these pathogens in the general population. In this study, upper respiratory samples (n = 1311) were collected cross-sectionally during winter from 11- and 24-month old children, their parents, and adults ≥60 years of age that were recruited irrespective of seeking medical care. Almost all children, approximately two-thirds of parents and a quarter of older adults tested positive for at least one pathogen, often in the absence of symptoms. Viral interference was evident for the combination of rhinovirus and respiratory syncytial virus. Attending childcare facilities and having siblings associated with increased pathogen counts in children. On average, children showed increased levels of mucosal cytokines compared to parents and especially proinflammatory molecules associated with the presence of symptoms. These findings may guide further research into transmission patterns of respiratory pathogens and assist in determining the most appropriate strategies for the prediction and prevention of disease.

Difference in respiratory syncytial virus-specific Fc-mediated antibody effector functions between children and adults

Respiratory syncytial virus (RSV) infections are a major cause of bronchiolitis and pneumonia in infants and older adults, for which there is no known correlate of protection. Increasing evidence suggests that Fc-mediated antibody effector functions have an important role, but little is known about the development, heterogeneity, and durability of these functional responses. In light of future vaccine strategies, a clear view of the immunological background and differences between various target populations is of crucial importance. In this study, we have assessed both quantitative and qualitative aspects of RSV-specific serum antibodies, including IgG/IgA levels, IgG subclasses, antibody-dependent complement deposition, cellular phagocytosis, and NK cell activation (ADNKA). Samples were collected cross-sectionally in different age groups (11-, 24-, and 46-month-old children, adults, and older adults; n = 31-35 per group) and longitudinally following natural RSV infection in (older) adults (2-36 months post-infection; n = 10). We found that serum of 24-month-old children induces significantly lower ADNKA than the serum of adults (P < 0.01), which is not explained by antibody levels. Furthermore, in (older) adults we observed boosting of antibody levels and functionality at 2-3 months after RSV infection, except for ADNKA. The strongest decrease was subsequently observed within the first 9 months, after which levels remained relatively stable up to three years post-infection. Together, these data provide a comprehensive overview of the functional landscape of RSV-specific serum antibodies in the human population, highlighting that while antibodies reach adult levels already at a young age, ADNKA requires more time to fully develop.

Frailty is related to serum inflammageing markers: results from the VITAL study

Frailty describes an age-associated state in individuals with an increased vulnerability and less resilience against adverse outcomes. To score frailty, studies have employed the questionnaires, such as the SF-36 and EQ-5D-3L, or the Frailty Index, a composite score based on deficit accumulation. Furthermore, ageing of the immune system is often accompanied by a state of low-grade inflammation (inflammageing). Here, we aimed to associate 29 circulating markers of inflammageing with frailty measures in a prospective cohort study to understand the mechanisms underlying ageing.Frailty measures and inflammageing markers were assessed in 317 participants aged 25-90. We determined four different measures of frailty: the Frailty Index based on 31 deficits, the EQ-5D-3L and two physical domains of the SF-36. Serum/plasma levels of inflammageing markers and CMV/EBV seropositivity were measured using different techniques: Quanterix, Luminex or ELISA.All four measures of frailty strongly correlated with age and BMI. Nineteen biomarkers correlated with age, some in a linear fashion (IL-6, YKL-40), some only in the oldest age brackets (CRP), and some increased at younger ages and then plateaued (CCL2, sIL-6R). After correcting for age, biomarkers, such as IL-6, CRP, IL-1RA, YKL-40 and elastase, were associated with frailty. When corrected for BMI, the number of associations reduced further.In conclusion, inflammageing markers, particularly markers reflecting innate immune activation, are related to frailty. These findings indicate that health decline and the accumulation of deficits with age is accompanied with a low-grade inflammation which can be detected by specific inflammatory markers.

High Levels of Detection of Nonpneumococcal Species of Streptococcus in Saliva from Adults in the United States

While the sensitivity of detection of pneumococcal carriage can be improved by testing respiratory tract samples with quantitative PCR (qPCR), concerns have been raised regarding the specificity of this approach. We therefore investigated the reliability of the widely used lytA qPCR assay when applied to saliva samples from older adults in relation to a more specific qPCR assay (piaB). During the autumn/winter seasons of 2018/2019 and 2019/2020, saliva was collected at multiple time points from 103 healthy adults aged 21 to 39 (n = 34) and >64 (n = 69) years (n = 344 total samples). Following culture enrichment, extracted DNA was tested using qPCR for piaB and lytA. By sequencing the variable region of rpsB (S2 typing), we identified the species of bacteria isolated from samples testing lytA-positive only. While 30 of 344 (8.7%) saliva samples (16.5% individuals) tested qPCR-positive for both piaB and lytA, 52 (15.1%) samples tested lytA-positive only. No samples tested piaB-positive only. Through extensive reculture attempts of the lytA-positive samples collected in 2018/2019, we isolated 23 strains (in 8 samples from 5 individuals) that were also qPCR-positive for only lytA. Sequencing determined that Streptococcus mitis and Streptococcus infantis were predominantly responsible for this lytA-positive qPCR signal. We identified a comparatively large proportion of samples generating positive signals with the widely used lytA qPCR and identified nonpneumococcal Streptococcus species responsible for this signal. This highlights the importance of testing for the presence of multiple gene targets in tandem for reliable and specific detection of pneumococcus in polymicrobial respiratory tract samples. IMPORTANCE Testing saliva samples with quantitative PCR (qPCR) improves the sensitivity of detection of pneumococcal carriage. The qPCR assay targeting lytA, the gene encoding the major pneumococcal autolysin, has become widely accepted for the identification of pneumococcus and is even considered the "gold standard" by many. However, when applying this approach to investigate the prevalence of pneumococcal carriage in adults in New Haven, CT, USA, we identified nonpneumococcal Streptococcus spp. that generate positive signals in this widely used assay. By testing also for piaB (encoding the iron acquisition ABC transporter lipoprotein, PiaB), our findings demonstrate the importance of testing for the presence of multiple gene targets in tandem for reliable molecular detection of pneumococcus in respiratory tract samples; targeting only lytA may lead to an overestimation of true carriage rates.

Incidence of Respiratory Syncytial Virus Infection in Older Adults: Limitations of Current Data

INTRODUCTION

Respiratory syncytial virus (RSV) is an important cause of severe respiratory illness in older adults and adults with respiratory or cardiovascular comorbidities. Published estimates of its incidence and prevalence in adult groups vary widely. This article reviews the potential limitations affecting RSV epidemiology studies and suggests points to consider when evaluating or designing them.

METHODS

Studies reporting the incidence or prevalence of RSV infection in adults in high-income Western countries from 2000 onwards were identified via a rapid literature review. Author-reported limitations were recorded, together with presence of other potential limitations. Data were synthesized narratively, with a focus on factors affecting incidence estimates for symptomatic infection in older adults.

RESULTS

A total of 71 studies met the inclusion criteria, most in populations with medically attended acute respiratory illness (ARI). Only a minority used case definitions and sampling periods tailored specifically to RSV; many used influenza-based or other criteria that are likely to result in RSV cases being missed. The great majority relied solely on polymerase chain reaction (PCR) testing of upper respiratory tract samples, which is likely to miss RSV cases compared with dual site sampling and/or addition of serology. Other common limitations were studying a single season, which has potential for bias due to seasonal variability; failure to stratify results by age, which underestimates the burden of severe disease in older adults; limited generalizability beyond a limited study setting; and absence of measures of uncertainty in the reporting of results.

CONCLUSIONS

A significant proportion of studies are likely to underestimate the incidence of RSV infection in older adults, although the effect size is unclear and there is also potential for overestimation. Well-designed studies, together with increased testing for RSV in patients with ARI in clinical practice, are required to accurately capture both the burden of RSV and the potential public health impact of vaccines.

Identification of aging-associated immunotypes and immune stability as indicators of post-vaccination immune activation

Immunosenescence describes immune dysfunction observed in older individuals. To identify individuals at-risk for immune dysfunction, it is crucial to understand the diverse immune phenotypes and their intrinsic functional capabilities. We investigated immune cell subsets and variation in the aging population. We observed that inter-individual immune variation was associated with age and cytomegalovirus seropositivity. Based on the similarities of immune subset composition among individuals, we identified nine immunotypes that displayed different aging-associated immune signatures, which explained inter-individual variation better than age. Additionally, we correlated the immune subset composition of individuals over approximately a year as a measure of stability of immune parameters. Immune stability was significantly lower in immunotypes that contained aging-associated immune subsets and correlated with a circulating CD38 + CD4+ T follicular helper cell increase 7 days after influenza vaccination. In conclusion, immune stability is a feature of immunotypes and could be a potential indicator of post-vaccination cellular kinetics.

Roles for Pathogen Interference in Influenza Vaccination, with Implications to Vaccine Effectiveness (VE) and Attribution of Influenza Deaths

Pathogen interference is the ability of one pathogen to alter the course and clinical outcomes of infection by another. With up to 3000 species of human pathogens the potential combinations are vast. These combinations operate within further immune complexity induced by infection with multiple persistent pathogens, and by the role which the human microbiome plays in maintaining health, immune function, and resistance to infection. All the above are further complicated by malnutrition in children and the elderly. Influenza vaccination offers a measure of protection for elderly individuals subsequently infected with influenza. However, all vaccines induce both specific and non-specific effects. The specific effects involve stimulation of humoral and cellular immunity, while the nonspecific effects are far more nuanced including changes in gene expression patterns and production of small RNAs which contribute to pathogen interference. Little is known about the outcomes of vaccinated elderly not subsequently infected with influenza but infected with multiple other non-influenza winter pathogens. In this review we propose that in certain years the specific antigen mix in the seasonal influenza vaccine inadvertently increases the risk of infection from other non-influenza pathogens. The possibility that vaccination could upset the pathogen balance, and that the timing of vaccination relative to the pathogen balance was critical to success, was proposed in 2010 but was seemingly ignored. Persons vaccinated early in the winter are more likely to experience higher pathogen interference. Implications to the estimation of vaccine effectiveness and influenza deaths are discussed.

Pneumococcal genetic variability in age-dependent bacterial carriage

The characteristics of pneumococcal carriage vary between infants and adults. Host immune factors have been shown to contribute to these age-specific differences, but the role of pathogen sequence variation is currently less well-known. Identification of age-associated pathogen genetic factors could leadto improved vaccine formulations. We therefore performed genome sequencing in a large carriage cohort of children and adults and combined this with data from an existing age-stratified carriage study. We compiled a dictionary of pathogen genetic variation, including serotype, strain, sequence elements, single-nucleotide polymorphisms (SNPs), and clusters of orthologous genes (COGs) for each cohort - all of which were used in a genome-wide association with host age. Age-dependent colonization showed weak evidence of being heritable in the first cohort (h2 = 0.10, 95% CI 0.00-0.69) and stronger evidence in the second cohort (h2 = 0.56, 95% CI 0.23-0.87). We found that serotypes and genetic background (strain) explained a proportion of the heritability in the first cohort (h2serotype = 0.07, 95% CI 0.04-0.14 and h2GPSC = 0.06, 95% CI 0.03-0.13) and the second cohort (h2serotype = 0.11, 95% CI 0.05-0.21 and h2GPSC = 0.20, 95% CI 0.12-0.31). In a meta-analysis of these cohorts, we found one candidate association (p=1.2 × 10-9) upstream of an accessory Sec-dependent serine-rich glycoprotein adhesin. Overall, while we did find a small effect of pathogen genome variation on pneumococcal carriage between child and adult hosts, this was variable between populations and does not appear to be caused by strong effects of individual genes. This supports proposals for adaptive future vaccination strategies that are primarily targeted at dominant circulating serotypes and tailored to the composition of the pathogen populations.

How influenza vaccination and virus interference may impact combined influenza-coronavirus disease burden

Demand for influenza vaccine rose as countries prepared for the second COVID-19 wave over the winter months of 2020-2021. High coverage of the influenza vaccine can significantly reduce morbidity and mortality of the burden of influenza. Natural influenza infection creates short-term non-specific immunity against respiratory viruses (virus interference). We model two viral diseases, both of the SEIR type, to investigate whether the influenza vaccine increases the combined disease burden of influenza and COVID-19 in a dual outbreak. We show that the combined disease burden’s behavior depends on virus interference factors and the proportion of the population vaccinated against influenza. Our results indicate that influenza vaccination only lowers the overall disease burden when net virus interference is relatively low.

Co-Expression of TIGIT and Helios Marks Immunosenescent CD8+ T Cells During Aging

Aging leads to alterations in the immune system that result in ineffective responsiveness against pathogens. Features of this process, collectively known as immunosenescence, accumulate in CD8⁺ T cells with age and have been ascribed to differentiation of these cells during the course of life. Here we aimed to identify novel markers in CD8⁺ T cells associated with immunosenescence. Furthermore, we assessed how these markers relate to the aging-related accumulation of highly differentiated CD27^-CD28^- cells. We found that co-expression of the transcription factor Helios and the aging-related marker TIGIT identifies CD8⁺ T cells that fail to proliferate and show impaired induction of activation markers CD69 and CD25 in response to stimulation in vitro. Despite this, in blood of older adults we found TIGIT⁺Helios⁺ T cells to become highly activated during an influenza-A virus infection, but these higher frequencies of activated TIGIT⁺Helios⁺ T cells associate with longer duration of coughing. Moreover, in healthy individuals, we found that TIGIT⁺Helios⁺ CD8⁺ T cells accumulate with age in the highly differentiated CD27^-CD28^- population. Interestingly, TIGIT⁺Helios⁺ CD8⁺ T cells also accumulate with age among the less differentiated CD27⁺CD28^- T cells before their transit into the highly differentiated CD27^-CD28^- stage. This finding suggests that T cells with immunosenescent features become prominent at old age also within the earlier differentiation states of these cells. Our findings show that co-expression of TIGIT and Helios refines the definition of immunosenescent CD8⁺ T cells and challenge the current dogma of late differentiation stage as proxy for T-cell immunosenescence.

System Complexity in Influenza Infection and Vaccination: Effects upon Excess Winter Mortality

Unexpected outcomes are usually associated with interventions in complex systems. Excess winter mortality (EWM) is a measure of the net effect of all competing forces operating each winter, including influenza(s) and non-influenza pathogens. In this study over 2400 data points from 97 countries are used to look at the net effect of influenza vaccination rates in the elderly aged 65+ against excess winter mortality (EWM) each year from the winter of 1980/81 through to 2019/20. The observed international net effect of influenza vaccination ranges from a 7.8% reduction in EWM estimated at 100% elderly vaccination for the winter of 1989/90 down to a 9.3% increase in EWM for the winter of 2018/19. The average was only a 0.3% reduction in EWM for a 100% vaccinated elderly population. Such outcomes do not contradict the known protective effect of influenza vaccination against influenza mortality per se—they merely indicate that multiple complex interactions lie behind the observed net effect against all-causes (including all pathogen causes) of winter mortality. This range from net benefit to net disbenefit is proposed to arise from system complexity which includes environmental conditions (weather, solar cycles), the antigenic distance between constantly emerging circulating influenza clades and the influenza vaccine makeup, vaccination timing, pathogen interference, and human immune diversity (including individual history of host-virus, host-antigen interactions and immunosenescence) all interacting to give the observed outcomes each year. We propose that a narrow focus on influenza vaccine effectiveness misses the far wider complexity of winter mortality. Influenza vaccines may need to be formulated in different ways, and perhaps administered over a shorter timeframe to avoid the unanticipated adverse net outcomes seen in around 40% of years.

Contribution of Influenza Viruses, Other Respiratory Viruses and Viral Co-Infections to Influenza-like Illness in Older Adults

Influenza-like illness (ILI) can be caused by a range of respiratory viruses. The present study investigates the contribution of influenza and other respiratory viruses, the occurrence of viral co-infections, and the persistence of the viruses after ILI onset in older adults. During the influenza season 2014-2015, 2366 generally healthy community-dwelling older adults (≥60 years) were enrolled in the study. Viruses were identified by multiplex ligation-dependent probe-amplification assay in naso- and oropharyngeal swabs taken during acute ILI phase, and 2 and 8 weeks later. The ILI incidence was 10.7%, which did not differ between vaccinated and unvaccinated older adults; influenza virus was the most frequently detected virus (39.4%). Other viruses with significant contribution were: rhinovirus (17.3%), seasonal coronavirus (9.8%), respiratory syncytial virus (6.7%), and human metapneumovirus (6.3%). Co-infections of influenza virus with other viruses were rare. The frequency of ILI cases in older adults in this 2014-2015 season with low vaccine effectiveness was comparable to that of the 2012-2013 season with moderate vaccine efficacy. The low rate of viral co-infections observed, especially for influenza virus, suggests that influenza virus infection reduces the risk of simultaneous infection with other viruses. Viral persistence or viral co-infections did not affect the clinical outcome of ILI.

Associations and recovery dynamics of the nasopharyngeal microbiota during influenza-like illness in the aging population

Influenza-like illness (ILI), a disease caused by respiratory pathogens including influenza virus, is a major health concern in older adults. There is little information on changes and recovery dynamics of the nasopharyngeal (NP) microbiota of older adults associated with an ILI. Here, we compared the NP microbiota in older adults reporting (n = 240) or not (n = 157) ILI during the 2014-2015 influenza season at different times of the ILI event. A small but significant effect of the ILI was observed on the microbiota community composition and structure when compared to controls and samples collected at recovery. Corynebacterium was negatively associated with ILI and its abundance increased after recovery. Potential pathobionts such as Haemophilus, Porphyromonas and Gemella had higher abundances during acute-ILI. Stability and changes in the NP microbial community showed individual dynamics. Key core genera, Corynebacterium, Moraxella and Dolosigranulum exhibited higher inter-individual variability in acute-ILI, but showed comparable variability to controls after recovery. Participants in the ILI group with higher core microbiota abundances at the acute phase showed higher microbiota stability after recovery. Our findings demonstrate that acute-ILI is associated with alterations in the phylogenetic structure of the NP microbiota in older adults. The variation in the core microbiota suggests imbalances in the ecosystem, which could potentially play a role in the susceptibility and recovery of the NP microbiota after an ILI event.

World Health Organization Influenza-Like Illness Underestimates the Burden of Respiratory Syncytial Virus Infection in Community-Dwelling Older Adults

Background

Respiratory syncytial virus (RSV) surveillance is heavily dependent on the influenza-like illness (ILI) case definition from the World Health Organization (WHO). Because ILI includes fever in its syndromic case definition, its ability to accurately identify acute respiratory tract infections (ARTI) caused by RSV in older adults is uncertain.

Methods

The accuracy of the WHO ILI and a modified ILI (requiring only self-reported fever) case definitions in identifying patients with PCR-confirmed RSV-ARTI was evaluated in community-dwelling older adults (≥60 years) from the prospective European RESCEU cohort study.

Results

Among 1040 participants, 750 ARTI episodes were analyzed including 36 confirmed RSV-ARTI. Due to a general lack of fever, sensitivity for RSV-ARTI was 33% for modified ILI and 11% for ILI. The area under the curve for both ILI definitions was 0.52 indicating poor discrimination for RSV. RSV-ARTI could not be distinguished from all other ARTI based on clinical symptoms.

Conclusions

The use of ILI underestimated the occurrence of RSV-ARTI in community-dwelling older adults up to 9-fold (11% sensitivity). Because worldwide RSV surveillance depends largely on ILI, there is an urgent need for a better approach to measure the occurrence of RSV disease and the impact of future RSV vaccine introduction.

Clinical Trials Registration. NCT03621930.

Incidence of Medically Attended Acute Respiratory Illnesses Due to Respiratory Viruses Across the Life Course During the 2018/19 Influenza Season

Background

While multiple respiratory viruses circulate in humans, few studies have compared the incidence of different viruses across the life course. We estimated the incidence of outpatient illness due to 12 different viruses during November 2018 through April 2019 in a fully enumerated population.

Methods

We conducted active surveillance for ambulatory care visits for acute respiratory illness (ARI) among members of Kaiser Permanente Washington (KPWA). Enrolled patients provided respiratory swab specimens which were tested for 12 respiratory viruses using RT-PCR. We estimated the cumulative incidence of infection due to each virus overall and by age group.

Results

The KPWA population under surveillance included 202,562 individuals, of whom 2,767 (1.4%) were enrolled in the study. Influenza A(H3N2) was the most commonly detected virus, with an overall incidence 21 medically attended illnesses per 1,000 population; the next most common viruses were influenza A(H1N1) (18 per 1,000), coronaviruses (13 per 1,000), respiratory syncytial virus (RSV, 13 per 1,000), and rhinovirus (9 per 1,000). RSV was the most common cause of medically attended ARI among children aged 1-4 years; coronaviruses were the most common among adults aged ≥65 years.

Conclusions

Consistent with other studies focused on single viruses, we found that influenza and RSV were major causes of acute respiratory illness in persons of all ages. In comparison, coronaviruses and rhinovirus were also important pathogens. Prior to the emergence of SARS-CoV-2, coronaviruses were the second-most common cause of medically attended ARI during the 2018/19 influenza season.

Efficacy and Safety of a Modified Vaccinia Ankara-NP+M1 Vaccine Combined with QIV in People Aged 65 and Older: A Randomised Controlled Clinical Trial (INVICTUS)

BACKGROUND

Pre-existing T cell responses to influenza have been correlated with improved clinical outcomes in natural history and human challenge studies. We aimed to determine the efficacy, safety and immunogenicity of a T-cell directed vaccine in older people.

METHODS

This was a multicentre, participant- and safety assessor-blinded, randomised, placebo-controlled trial of the co-administration of Modified Vaccinia Ankara encoding nucleoprotein and matrix protein 1 (MVA-NP+M1) and annual influenza vaccine in participants ≥ 65. The primary outcome was the number of days with moderate or severe influenza-like symptoms (ILS) during the influenza season.

RESULTS

846 of a planned 2030 participants were recruited in the UK prior to, and throughout, the 2017/18 flu season. There was no evidence of a difference in the reported rates of days of moderate or severe ILS during influenza-like illness episodes (unadjusted OR = 0.95, 95% CI: 0.54-1.69; adjusted OR = 0.91, 95% CI: 0.51-1.65). The trial was stopped after one season due to a change in the recommended annual flu vaccine, for which safety of the new combination had not been established. More participants in the MVA-NP+M1 group had transient moderate or severe pain, redness, and systemic responses in the first seven days.

CONCLUSION

The MVA-NP+M1 vaccine is well tolerated in those aged 65 years and over. Larger trials would be needed to determine potential efficacy.

Regulatory KIR+ RA+ T cells accumulate with age and are highly activated during viral respiratory disease

Severe respiratory viral infectious diseases such as influenza and COVID‐19 especially affect the older population. This is partly ascribed to diminished CD8⁺ T‐cell responses a result of aging. The phenotypical diversity of the CD8⁺ T‐cell population has made it difficult to identify the impact of aging on CD8⁺ T‐cell subsets associated with diminished CD8⁺ T‐cell responses. Here we identify a novel human CD8⁺ T‐cell subset characterized by expression of Killer‐cell Immunoglobulin‐like Receptors (KIR⁺) and CD45RA (RA⁺). These KIR⁺RA⁺ T cells accumulated with age in the blood of healthy individuals (20–82 years of age, n = 50), expressed high levels of aging‐related markers of T‐cell regulation, and were functionally capable of suppressing proliferation of other CD8⁺ T cells. Moreover, KIR⁺RA⁺ T cells were a major T‐cell subset becoming activated in older adults suffering from an acute respiratory viral infection (n = 36), including coronavirus and influenza virus infection. In addition, older adults with influenza A infection showed that higher activation status of their KIR⁺RA⁺ T cells associated with longer duration of respiratory symptoms. Together, our data indicate that KIR⁺RA⁺ T cells are a unique human T‐cell subset with regulatory properties that may explain susceptibility to viral respiratory disease at old age.

Impact of influenza vaccination in the Netherlands, 2007-2016: Vaccinees consult their general practitioner for clinically diagnosed influenza, acute respiratory infections, and pneumonia more often than non-vaccinees

Introduction

We aimed to develop an innovative population-based method to estimate the health effect of influenza vaccination based on electronic medical records collected within a general practitioner (GP)-based influenza surveillance system in the Netherlands.

Methods

In each season between 2006/07 and 2015/16, we fitted multilevel Poisson regression models to compare GP consultation rates for clinically diagnosed influenza, acute respiratory infections (ARI), pneumonia, and lower back pain (as a control) between vaccinated vs. unvaccinated individuals. Season-specific relative risks and 95% confidence intervals (CI) were pooled into summary risk ratio (SRR) through random-effects meta-analysis models. Analyses were stratified by patient age (<45, 45–59, 60–74, ≥75 years) and medical indication for the vaccine (any vs. none, subjects aged ≤60 years only).

Results

Overall, 12.6% and 21.4% of study subjects were vaccinated because of their age only or because of an underlying medical condition. Vaccine uptake declined over time, especially among subjects aged ≤74 years with medical indications for vaccination. Vaccinated individuals had significantly higher GP consultation rates for clinically diagnosed influenza (SRR 1.24, 95% CI 1.12–1.38, p-value <0.001), ARI (SRR 1.33, 95% CI 1.27–1.39, p-value <0.001), pneumonia (SRR 1.27, 95% CI 1.19–1.36, p-value <0.001), and lower back pain (SRR 1.21, 95% CI 1.14–1.28, p-value <0.001) compared to unvaccinated individuals.

Discussion

Contrary to expectations, influenza vaccinees have GP consultation rates for clinically diagnosed influenza, ARI and pneumonia that are 24–33% higher compared to unvaccinated individuals. The lower back pain finding suggests that the increase in consultation rates is partially caused by confounding. Importantly, considering the data are not laboratory-confirmed, our results cannot be linked directly to influenza, but only to respiratory illnesses in general.

Latent CMV Infection Is Associated With Lower Influenza Virus-Specific Memory T-Cell Frequencies, but Not With an Impaired T-Cell Response to Acute Influenza Virus Infection

Latent infection with cytomegalovirus (CMV) is assumed to contribute to the age-associated decline of the immune system. CMV induces large changes in the T-cell pool and may thereby affect other immune responses. CMV is expected to impact especially older adults, who are already at higher risk of severe disease and hospitalization upon infections such as influenza virus (IAV) infection. Here, we investigated the impact of CMV infection on IAV-specific CD8⁺ T-cell frequencies in healthy individuals (n=96) and the response to IAV infection in older adults (n=72). IAV-specific memory T-cell frequencies were lower in healthy CMV⁺ older individuals compared to healthy CMV^- older individuals. Upon acute IAV infection, CMV serostatus or CMV-specific antibody levels were not negatively associated with IAV-specific T-cell frequencies, function, phenotype or T-cell receptor repertoire diversity. This suggests that specific T-cell responses upon acute IAV infection are not negatively affected by CMV. In addition, we found neither an association between CMV infection and inflammatory cytokine levels in serum during acute IAV infection nor between cytokine levels and the height of the IAV-specific T-cell response upon infection. Finally, CMV infection was not associated with increased severity of influenza-related symptoms. In fact, CMV infection was even associated with increased IAV-specific T-cell responses early upon acute IAV infection. In conclusion, although associated with lower frequencies of memory IAV-specific T cells in healthy individuals, CMV infection does not seem to hamper the induction of a proper T-cell response during acute IAV infection in older adults.

Burden of infections on older patients presenting to general practice: a registry-based study

BACKGROUND

Estimates on the incidence rates of infections are needed to assess the burden of disease in the community.

OBJECTIVE

To assess incidence rates of potentially serious infections in patients aged 65 years and over presenting to Flemish general practice from 2000 to 2015, and to describe patient characteristics.

METHODS

We performed a retrospective study, based on data provided by the Intego morbidity registry of the KU Leuven, which includes the electronic medical records of 111 general practitioners. Incidence rates were calculated taking person-time at risk into account, and longitudinal trends from 2000 to 2015 were analysed using autoregressive time-series analyses.

RESULTS

On average, a person aged 65 years or older has an 8.0% risk of getting a potentially serious infection each year. Acute cystitis was the most often occurring potentially serious infection [39.8/1000 person-years; 95% confidence interval (CI): 39.4-40.2], followed by influenza like illness (ILI, 24.3/1000 person-years; 95% CI: 24.0-24.6) and pneumonia (9.7/1000 person-years; 95% CI: 9.5-9.9). The incidence rates of pneumonia were higher in older age groups and in men, whereas they were markedly lower for ILI at older ages, in both genders. From 2000 to 2015, overall incidence rates decreased significantly for ILI, while they increased in women for pneumonia, acute cystitis and pyelonephritis. Common chronic comorbidities were non-insulin dependent diabetes, chronic obstructive pulmonary disease, asthma, heart failure and chronic renal insufficiency.

CONCLUSIONS

Potentially serious infections are quite common in an older patient population presenting to primary care. They are accompanied by several chronic comorbidities, which may differ by infection type.

Accurate serology for SARS-CoV-2 and common human coronaviruses using a multiplex approach

Serology is a crucial part of the public health response to the ongoing SARS-CoV-2 pandemic. Here, we describe the development, validation and clinical evaluation of a protein micro-array as a quantitative multiplex immunoassay that can identify S and N-directed SARS-CoV-2 IgG antibodies with high specificity and sensitivity and distinguish them from all currently circulating human coronaviruses. The method specificity was 100% for SARS-CoV-2 S1 and 96% for N antigen based on extensive syndromic (n=230 cases) and population panel (n=94) testing that also confirmed the high prevalence of seasonal human coronaviruses. To assess its potential role for both SARS-CoV-2 patient diagnostics and population studies, we evaluated a large heterogeneous COVID-19 cohort (n=330) and found an overall sensitivity of 89% (≥ 21 days post onset symptoms (dps)), ranging from 86% to 96% depending on severity of disease. For a subset of these patients longitudinal samples were provided up to 56 dps. Mild cases showed absent or delayed, and lower SARS-CoV-2 antibody responses. Overall, we present the development and extensive clinical validation of a multiplex coronavirus serological assay for syndromic testing, to answer research questions regarding to antibody responses, to support SARS-CoV-2 diagnostics and to evaluate epidemiological developments efficiently and with high-throughput.

Validation and clinical evaluation of a SARS-CoV-2 surrogate virus neutralisation test (sVNT)

To understand SARS-CoV-2 immunity after natural infection or vaccination, functional assays such as virus neutralising assays are needed. So far, assays to detect SARS-CoV-2 neutralising antibodies rely on cell-culture based infection assays either using wild type SARS-CoV-2 or pseudotyped viruses. Such assays are labour-intensive, require appropriate biosafety facilities and are difficult to standardize. Recently, a new surrogate virus neutralisation test (sVNT) was described that uses the principle of an ELISA to measure the neutralisation capacity of anti-SARS-CoV-2 antibodies directed against the receptor binding domain. Here, we performed an independent evaluation of the robustness, specificity and sensitivity on an extensive panel of sera from 269 PCR-confirmed COVID-19 cases and 259 unmatched samples collected before 2020 and compared it to cell-based neutralisation assays. We found a high specificity of 99.2 (95%CI: 96.9–99.9) and overall sensitivity of 80.3 (95%CI: 74.9–84.8) for the sVNT. Clinical sensitivity increased between early (<14 days post symptom onset or post diagnosis, dpos/dpd) and late sera (>14 dpos/dpd) from 75.0 (64.7–83.2) to 83.1 (76.5–88.1). Also, higher severity was associated with an increase in clinical sensitivity. Upon comparison with cell-based neutralisation assays we determined an analytical sensitivity of 74.3 (56.4–86.9) and 98.2 (89.4–99.9) for titres ≥10 to <40 and ≥40 to <160, respectively. Only samples with a titre ≥160 were always positive in the sVNT. In conclusion, the sVNT can be used as an additional assay to determine the immune status of COVID-19 infected of vaccinated individuals but its value needs to be assessed for each specific context.

Influenza-like Illness Exacerbates Pneumococcal Carriage in Older Adults

BACKGROUND

In older adults pneumococcal disease is strongly associated with respiratory viral infections, but the impact of viruses on Streptococcus pneumoniae carriage prevalence and load remains poorly understood. Here, we investigated the effects of influenza-like illness (ILI) on pneumococcal carriage in community-dwelling older adults.

METHODS

We investigated the presence of pneumococcal DNA in saliva samples collected in the 2014/2015 influenza season from 232 individuals aged ≥60 years at ILI-onset, followed by sampling 2-3 weeks and 7-9 weeks after the first sample. We also sampled 194 age-matched controls twice 2-3 weeks apart. Pneumococcal DNA was detected with quantitative-PCRs targeting piaB and lytA genes in raw and in culture-enriched saliva. Bacterial and pneumococcal abundances were determined in raw saliva with 16S and piaB quantification.

RESULTS

The prevalence of pneumococcus-positive samples was highest at onset of ILI (18% or 42/232) and lowest among controls (13% or 26/194, and 11% or 22/194, at the first and second sampling moment, respectively), though these differences were not significant. Pneumococcal carriage was associated with exposure to young children (OR:2.71, 95%CI 1.51-5.02, p<0.001), and among asymptomatic controls with presence of rhinovirus infection (OR:4.23; 95%CI 1.16-14.22, p<0.05). When compared with carriers among controls, pneumococcal absolute abundances were significantly higher at onset of ILI (p<0.01), and remained elevated beyond recovery from ILI (p<0.05). Finally, pneumococcal abundances were highest in carriage events newly-detected after ILI-onset (estimated geometric mean 1.21E -5, 95%CI 2.48E -7-2.41E -5, compared with pre-existing carriage).

CONCLUSIONS

ILI exacerbates pneumococcal colonization of the airways in older adults, and this effect persists beyond recovery from ILI.

SARS-CoV-2-Specific Antibody Detection for Seroepidemiology: A Multiplex Analysis Approach Accounting for Accurate Seroprevalence

Background

The COVID-19 pandemic necessitates better understanding of the kinetics of antibody production induced by infection with SARS-CoV-2. We aimed to develop a high-throughput multiplex assay to detect antibodies to SARS-CoV-2 to assess immunity to the virus in the general population.

Methods

Spike protein subunits S1 and receptor binding domain, and nucleoprotein were coupled to microspheres. Sera collected before emergence of SARS-CoV-2 (n = 224) and of non-SARS-CoV-2 influenza-like illness (n = 184), and laboratory-confirmed cases of SARS-CoV-2 infection (n = 115) with various severities of COVID-19 were tested for SARS-CoV-2–specific IgG concentrations.

Results

Our assay discriminated SARS-CoV-2–induced antibodies and those induced by other viruses. The assay specificity was 95.1%–99.0% with sensitivity 83.6%–95.7%. By merging the test results for all 3 antigens a specificity of 100% was achieved with a sensitivity of at least 90%. Hospitalized COVID-19 patients developed higher IgG concentrations and the rate of IgG production increased faster compared to nonhospitalized cases.

Conclusions

The bead-based serological assay for quantitation of SARS-CoV-2–specific antibodies proved to be robust and can be conducted in many laboratories. We demonstrated that testing of antibodies against multiple antigens increases sensitivity and specificity compared to single-antigen–specific IgG determination.

Substantial underestimation of SARS-CoV-2 infection in the United States

Accurate estimates of the burden of SARS-CoV-2 infection are critical to informing pandemic response. Confirmed COVID-19 case counts in the U.S. do not capture the total burden of the pandemic because testing has been primarily restricted to individuals with moderate to severe symptoms due to limited test availability. Here, we use a semi-Bayesian probabilistic bias analysis to account for incomplete testing and imperfect diagnostic accuracy. We estimate 6,454,951 cumulative infections compared to 721,245 confirmed cases (1.9% vs. 0.2% of the population) in the United States as of April 18, 2020. Accounting for uncertainty, the number of infections during this period was 3 to 20 times higher than the number of confirmed cases. 86% (simulation interval: 64-99%) of this difference is due to incomplete testing, while 14% (0.3-36%) is due to imperfect test accuracy. The approach can readily be applied in future studies in other locations or at finer spatial scale to correct for biased testing and imperfect diagnostic accuracy to provide a more realistic assessment of COVID-19 burden.

Antibody and Local Cytokine Response to Respiratory Syncytial Virus Infection in Community-Dwelling Older Adults

Respiratory syncytial virus (RSV) can cause severe morbidity and mortality in certain risk groups, especially infants and older adults. Currently no (prophylactic) treatment is available, except for a partially effective yet highly expensive monoclonal antibody. RSV therefore remains a major public health concern. To allow targeted development of novel vaccines and therapeutics, it is of great importance to understand the immunological mechanisms that underlie (protection from) severe disease in specific risk populations. Since most RSV-related studies focus on infants, there are only very limited data available concerning the response to RSV in the elderly population. Therefore, in this study, RSV-induced antibody responses and local cytokine secretion were assessed in community-dwelling older adults. These data provide novel insights that will benefit ongoing efforts to design safe and effective prevention and treatment strategies for RSV in an understudied risk group.

Respiratory syncytial virus (RSV) is increasingly recognized for causing severe morbidity and mortality in older adults, but there are few studies on the RSV-induced immune response in this population. Information on the immunological processes at play during RSV infection in specific risk groups is essential for the rational and targeted design of novel vaccines and therapeutics. Here, we assessed the antibody and local cytokine response to RSV infection in community-dwelling older adults (≥60 years of age). During three winters, serum and nasopharyngeal swab samples were collected from study participants during acute respiratory infection and recovery. RSV IgG enzyme-linked immunosorbent assays (ELISA) and virus neutralization assays were performed on serum samples from RSV-infected individuals (n = 41) and controls (n = 563 and n = 197, respectively). Nasal RSV IgA and cytokine concentrations were determined using multiplex immunoassays in a subset of participants. An in vitro model of differentiated primary bronchial epithelial cells was used to assess RSV-induced cytokine responses over time. A statistically significant increase in serum neutralization titers and IgG concentrations was observed in RSV-infected participants compared to controls. During acute RSV infection, a statistically significant local upregulation of beta interferon (IFN-β), IFN-λ1, IFN-γ, interleukin 1β (IL-1β), tumor necrosis factor alpha (TNF-α), IL-6, IL-10, CXCL8, and CXCL10 was found. IFN-β, IFN-λ1, CXCL8, and CXCL10 were also upregulated in the epithelial model upon RSV infection. In conclusion, this study provides novel insights into the basic immune response to RSV infection in an important and understudied risk population, providing leads for future studies that are essential for the prevention and treatment of severe RSV disease in older adults.

IMPORTANCE Respiratory syncytial virus (RSV) can cause severe morbidity and mortality in certain risk groups, especially infants and older adults. Currently no (prophylactic) treatment is available, except for a partially effective yet highly expensive monoclonal antibody. RSV therefore remains a major public health concern. To allow targeted development of novel vaccines and therapeutics, it is of great importance to understand the immunological mechanisms that underlie (protection from) severe disease in specific risk populations. Since most RSV-related studies focus on infants, there are only very limited data available concerning the response to RSV in the elderly population. Therefore, in this study, RSV-induced antibody responses and local cytokine secretion were assessed in community-dwelling older adults. These data provide novel insights that will benefit ongoing efforts to design safe and effective prevention and treatment strategies for RSV in an understudied risk group.

Determinants of Vaccination Uptake in Risk Populations: A Comprehensive Literature Review

Vaccination uptake has decreased globally in recent years, with a subsequent rise of vaccine-preventable diseases. Travellers, immunocompromised patients (ICP), and healthcare workers (HCW) are groups at increased risk for (severe) infectious diseases due to their behaviour, health, or occupation, respectively. While targeted vaccination guidelines are available, vaccination uptake seems low. In this review, we give a comprehensive overview of determinants-based on the integrated change model-predicting vaccination uptake in these groups. In travellers, low perceived risk of infection and low awareness of vaccination recommendations contributed to low uptake. Additionally, ICP were often unaware of the recommended vaccinations. A physician's recommendation is strongly correlated with higher uptake. Furthermore, ICP appeared to be mainly concerned about the risks of vaccination and fear of deterioration of their underlying disease. For HCW, perceived risk of (the severity of) infection for themselves and for their patients together with perceived benefits of vaccination contribute most to their vaccination behaviour. As the determinants that affect uptake are numerous and diverse, we argue that future studies and interventions should be based on multifactorial health behaviour models, especially for travellers and ICP as only a limited number of such studies is available yet.

In-depth immune cellular profiling reveals sex-specific associations with frailty

Background

With advancing age, the composition of leukocyte subpopulations in peripheral blood is known to change, but how this change differs between men and women and how it relates to frailty is poorly understood. Our aim in this exploratory study was to investigate whether frailty is associated with changes in immune cell subpopulations and whether this differs between men and women. Therefore, we performed in-depth immune cellular profiling by enumerating a total of 37 subpopulations of T cells, B cells, NK cells, monocytes, and neutrophils in peripheral blood of 289 elderly people between 60-87 years of age. Associations between frailty and each immune cell subpopulation were tested separately in men and women and were adjusted for age and CMV serostatus. In addition, a random forest algorithm was used to predict a participant’s frailty score based on enumeration of immune cell subpopulations.

Results

In the association study, frailty was found to be associated with increased numbers of neutrophils in both men and in women. Frailer women, but not men, showed higher numbers of total and CD16^- monocytes, and lower numbers of both CD56⁺ T cells and late differentiated CD4⁺ TemRA cells. The random forest algorithm confirmed all the findings of the association studies in men and women. In men, the predictive accuracy of the algorithm was too low (5.5%) to warrant additional conclusions on top of the ones derived from the association study. In women however, the predictive accuracy was higher (23.1%), additionally revealing that total T cell numbers and total lymphocyte numbers also contribute in predicting frailty.

Conclusions

In-depth immune cellular profiling revealed consistent associations of frailty with elevated numbers of myeloid cell subpopulations in both men and women. Furthermore, additional associations were found between frailty and lower numbers of some T cell subpopulations, in women only. Thus, our study indicates sex-specific associations of immune subpopulations with frailty. We hope that our study will prompt further investigation into the sex-specific immune mechanisms associated with the development of frailty.

The Impact of Influenza Vaccination on Antibiotic Use in the United States, 2010-2017

Background

Influenza, which peaks seasonally, is an important driver for antibiotic prescribing. Although influenza vaccination has been shown to reduce severe illness, evidence of the population-level effects of vaccination coverage on rates of antibiotic prescribing in the United States is lacking.

Methods

We conducted a retrospective analysis of influenza vaccination coverage and antibiotic prescribing rates from 2010 to 2017 across states in the United States, controlling for differences in health infrastructure and yearly vaccine effectiveness. Using data from IQVIA’s Xponent database and the US Centers for Disease Control and Prevention’s FluVaxView, we employed fixed-effects regression analysis to analyze the relationship between influenza vaccine coverage rates and the number of antibiotic prescriptions per 1000 residents from January to March of each year.

Results

We observed that, controlling for socioeconomic differences, access to health care, childcare centers, climate, vaccine effectiveness, and state-level differences, a 10–percentage point increase in the influenza vaccination rate was associated with a 6.5% decrease in antibiotic use, equivalent to 14.2 (95% CI, 6.0–22.4; P = .001) fewer antibiotic prescriptions per 1000 individuals. Increased vaccination coverage reduced prescribing rates the most in the pediatric population (0–18 years), by 15.2 (95% CI, 9.0–21.3; P < .001) or 6.0%, and the elderly (aged 65+), by 12.8 (95% CI, 6.5–19.2; P < .001) or 5.2%.

Conclusions

Increased influenza vaccination uptake at the population level is associated with state-level reductions in antibiotic use. Expanding influenza vaccination could be an important intervention to reduce unnecessary antibiotic prescribing.

Cost-effectiveness of inactivated influenza vaccination in children with medical risk conditions in the Netherlands

BACKGROUND

In many countries, annual immunization with inactivated influenza vaccine (IIV) is recommended for children with medical risk conditions. Prior cost-effectiveness analyses found such immunization to be cost saving, but assumed effectiveness against non-severe influenza outcomes and a higher effectiveness against severe influenza outcomes than recent studies would suggest. However, recent vaccine studies do not indicate any reduction in community or outpatient disease episodes in IIV immunized individuals. We therefore evaluated cost-effectiveness of IIV immunization in children with medical risk conditions in the Netherlands, assuming that IIV reduces influenza-related hospitalization and death, but has no meaningful impact on non-severe health outcomes.

METHODS

A health economic decision tree model was developed to evaluate health effects and costs of annual IIV immunization versus no immunization. Model inputs were based on our study on influenza-related primary care visits and other literature. Immunization was considered cost effective if associated costs were less than €20,000 per quality-adjusted life year (QALY) gained. Probabilistic sensitivity analyses were performed to assess robustness of results, and one-way sensitivity analyses and scenario analyses were done to assess the influence of individual parameters.

RESULTS

Annual IIV prevents an average of 1.59 influenza-related hospitalizations and 0.02 deaths per 1,000 children with medical risk conditions. This results in an expected QALY gain of 0.43 at incremental costs of €21,564 per 1,000 children, corresponding to an incremental cost-effectiveness ratio (ICER) of €50,297/QALY compared to no immunization. Under base case assumptions, immunization had a 5% probability of being cost effective. Results were most influenced by vaccine efficacy against fatal influenza, QALY loss due to death, and mortality rate.

CONCLUSIONS

If IIV only reduces severe disease outcomes, as current evidence suggests, annual immunization of medical risk children is unlikely to be cost effective. Results should however be interpreted with caution as cost-effectiveness is largely dependent on incidence and QALY losses for fatal influenza, for which evidence is scarce.

Immune surveillance for vaccine-preventable diseases

INTRODUCTION

Immunesurveillance is an important tool to monitor the protection of the population against vaccine-preventable diseases, which is currently mostly based on the detection of specific serum antibodies. However, the landscape of immune surveillance is changing, driven by emerging and evolving pathogens, changes in the age distribution of the population and scientific understanding of protective immunity, necessitating a comprehensive review.

AREAS COVERED

To anticipate these changes, reliable and high-throughput detection of antibody levels is desired to enable screening in larger population settings. Antibody levels alone do not always equate with protection and may require additional functional testing of the antibodies or immune cell-based assays. In addition, the location (systemic or locally mucosal) of the infection and whether the antibodies are induced through infection or vaccination have implications for both immune protection and assessing immune status.

EXPERT COMMENTARY

In order to perform multicenter studies on many samples for multiple antigens, more validated reference materials and wider adoption of high-throughput techniques are needed. The field of serosurveillance will also benefit from better correlates of protection and understanding of (local) mechanisms of protection. Here we give an overview of the current state-of-the-art of serosurveillance and how the field could move forward.

Validation of the Seegene RV15 multiplex PCR for the detection of influenza A subtypes and influenza B lineages during national influenza surveillance in hospitalized adults

Background. The Serious Outcomes Surveillance Network of the Canadian Immunization Research Network (CIRN SOS) has been performing active influenza surveillance since 2009 (ClinicalTrials.gov identifier: NCT01517191). Influenza A and B viruses are identified and characterized using real-time reverse-transcriptase polymerase chain reaction (RT-PCR), and multiplex testing has been performed on a subset of patients to identify other respiratory virus aetiologies. Since both methods can identify influenza A and B, a direct comparison was performed.Methods. Validated real-time RT-PCRs from the World Health Organization (WHO) to identify influenza A and B viruses, characterize influenza A viruses into the H1N1 or H3N2 subtypes and describe influenza B viruses belonging to the Yamagata or Victoria lineages. In a subset of patients, the Seeplex RV15 One-Step ACE Detection assay (RV15) kit was also used for the detection of other respiratory viruses.Results. In total, 1111 nasopharyngeal swabs were tested by RV15 and real-time RT-PCRs for influenza A and B identification and characterization. For influenza A, RV15 showed 98.0 % sensitivity, 100 % specificity and 99.7 % accuracy. The performance characteristics of RV15 were similar for influenza A subtypes H1N1 and H3N2. For influenza B, RV15 had 99.2 % sensitivity, 100 % specificity and 99.8 % accuracy, with similar assay performance being shown for both the Yamagata and Victoria lineages.Conclusions. Overall, the detection of circulating subtypes of influenza A and lineages of influenza B by RV15 was similar to detection by real-time RT-PCR. Multiplex testing with RV15 allows for a more comprehensive respiratory virus surveillance in hospitalized adults, without significantly compromising the reliability of influenza A or B virus detection.

Inactivated influenza vaccine does not reduce all cause respiratory illness in children with pre-existing medical conditions

BACKGROUND

The effectiveness of inactivated influenza vaccine (IIV) immunization in preventing all cause respiratory illness (RI) in children with pre-existing medical conditions has not been fully established and varies from season to season. This study aims to quantify the overall impact of IIV immunization on primary care attended RI episodes in children with pre-existing medical conditions, using robust observational data spanning twelve influenza seasons.

METHODS

Electronic records of IIV eligible children aged 6 months to 18 years were extracted from primary care databases over the years 2004-2015. IIV eligibility criteria according to Dutch guidelines included (chronic) respiratory and cardiovascular disease and diabetes mellitus. For each year, information on IIV immunization status, primary care attended RI episodes (including influenza, acute respiratory tract infections and asthma exacerbations) and potential confounders were collected. Generalized estimating equations were used to model the association between IIV status and occurrence of at least one RI episode during the influenza epidemic period with "current year immunized" as reference group. Robustness of findings were assessed by performing various sensitivity analyzes in which (i) seasons with a mismatch between the dominant circulating influenza virus and vaccine strain were excluded, (ii) influenza periods were further restricted to weeks with at least 30% influenza virus positive specimens in sentinel surveillance (instead of 5%), (iii) propensity scores were used to adjust for confounding.

RESULTS

In total, 11,797 children (follow-up duration: 38,701 child-years) were eligible for IIV for ≥ one season with 29% immunized at least once. The adjusted odds for primary care attended RI episodes during the influenza epidemic period did not differ between current season immunized versus not immunized children (adjusted OR:1.01; 95%CI:0.90-1.13). The various sensitivity analysis showed comparable results.

CONCLUSIONS

IIV immunization in children with pre-existing medical conditions does not reduce all cause RI episodes encountered in primary care during the influenza season.

Common cold in Team Finland during 2018 Winter Olympic Games (PyeongChang): epidemiology, diagnosis including molecular point-of-care testing (POCT) and treatment

Objectives

The common cold is the main cause of medical time loss in elite sport. Rapid diagnosis has been a challenge that may be amenable to molecular point-of-care testing (POCT).

Methods

We performed a prospective observational study of the common cold in Team Finland during the 2018 Winter Olympic Games. There were 44 elite athletes and 68 staff members. The chief physician recorded the symptoms of the common cold daily on a standardised form. Two nasal swabs were taken at the onset of symptoms. One swab was analysed within 45 min using a molecular POCT for respiratory syncytial virus and influenza A and B viruses. After the Games, the other swab was tested for 16 possible causative respiratory viruses using PCR in laboratory-based testing.

Results

20 out of 44 (45%) athletes and 22 out of 68 (32%) staff members experienced symptoms of the common cold during a median stay of 21 days. Eleven (26%) samples tested virus-positive using POCT. All subjects with influenza (n=6) and 32 close contacts were treated with oseltamivir. The aetiology of the common cold was finally detected in 75% of the athletes and 68 % of the staff members. Seven virus clusters were identified. They were caused by coronaviruses 229E, NL63 and OC43, influenza B virus, respiratory syncytial virus A, rhinovirus and human metapneumovirus. The virus infections spread readily within the team, most commonly within the same sport discipline.

Conclusions

The cold was indeed a common illness in Team Finland during the Winter Olympic Games. POCT proved to be clinically valuable, especially for influenza. The aetiology of the common cold was identified in most cases.

Joint sequencing of human and pathogen genomes reveals the genetics of pneumococcal meningitis

Streptococcus pneumoniae is a common nasopharyngeal colonizer, but can also cause life-threatening invasive diseases such as empyema, bacteremia and meningitis. Genetic variation of host and pathogen is known to play a role in invasive pneumococcal disease, though to what extent is unknown. In a genome-wide association study of human and pathogen we show that human variation explains almost half of variation in susceptibility to pneumococcal meningitis and one-third of variation in severity, identifying variants in CCDC33 associated with susceptibility. Pneumococcal genetic variation explains a large amount of invasive potential (70%), but has no effect on severity. Serotype alone is insufficient to explain invasiveness, suggesting other pneumococcal factors are involved in progression to invasive disease. We identify pneumococcal genes involved in invasiveness including pspC and zmpD, and perform a human-bacteria interaction analysis. These genes are potential candidates for the development of more broadly-acting pneumococcal vaccines.

Excess Deaths Attributable to Influenza-Like Illness in the ESRD Population

BACKGROUND

Morbidity and mortality vary seasonally. Timing and severity of influenza seasons contribute to those patterns, especially among vulnerable populations such as patients with ESRD. However, the extent to which influenza-like illness (ILI), a syndrome comprising a range of potentially serious respiratory tract infections, contributes to mortality in patients with ESRD has not been quantified.

METHODS

We used data from the Centers for Disease Control and Prevention (CDC) Outpatient Influenza-like Illness Surveillance Network and Centers for Medicare and Medicaid Services ESRD death data from 2000 to 2013. After addressing the increasing trend in deaths due to the growing prevalent ESRD population, we calculated quarterly relative mortality compared with average third-quarter (summer) death counts. We used linear regression models to assess the relationship between ILI data and mortality, separately for quarters 4 and 1 for each influenza season, and model parameter estimates to predict seasonal mortality counts and calculate excess ILI-associated deaths.

RESULTS

An estimated 1% absolute increase in quarterly ILI was associated with a 1.5% increase in relative mortality for quarter 4 and a 2.0% increase for quarter 1. The average number of annual deaths potentially attributable to ILI was substantial, about 1100 deaths per year.

CONCLUSIONS

We found an association between community ILI activity and seasonal variation in all-cause mortality in patients with ESRD, with ILI likely contributing to >1000 deaths annually. Surveillance efforts, such as timely reporting to the CDC of ILI activity within dialysis units during influenza season, may help focus attention on high-risk periods for this vulnerable population.

Nontypeable Haemophilus influenzae Invasive Blood Isolates Are Mainly Phosphorylcholine Negative and Show Decreased Complement-Mediated Killing That Is Associated with Lower Binding of IgM and CRP in Comparison to Colonizing Isolates from the Oropharynx

Nontypeable Haemophilus influenzae (NTHi) bacteria express various molecules that contribute to their virulence. The presence of phosphocholine (PCho) on NTHi lipooligosaccharide increases adhesion to epithelial cells and is an advantage for the bacterium, enabling nasopharyngeal colonization, as measured in humans and animal models. However, when PCho is expressed on the lipooligosaccharide, it is also recognized by the acute-phase protein C-reactive protein (CRP) and PCho-specific antibodies, both of which are potent initiators of the classical pathway of complement activation. In this study, we show that blood isolates, which are exposed to CRP and PCho-specific antibodies in the bloodstream, have a higher survival in serum than oropharyngeal isolates, which was associated with a decreased presence of PCho. PCho^low strains showed decreased IgM, CRP, and complement C3 deposition, which was associated with increased survival in human serum. Consistent with the case for the PCho^low strains, removal of PCho expression by licA gene deletion decreased IgM, CRP, and complement C3 deposition, which increased survival in human serum. Complement-mediated killing of PCho^high strains was mainly dependent on binding of IgM to the bacterial surface. These data support the hypothesis that a PCho^low phenotype was selected in blood during invasive disease, which increased resistance to serum killing, mainly due to lowered IgM and CRP binding to the bacterial surface.

Attitudes, believes, determinants and organisational barriers behind the low seasonal influenza vaccination uptake in healthcare workers - A cross-sectional survey

BACKGROUND

Seasonal influenza threatens hospitalised patients and residents of nursing homes annually. Due to age and chronic disease their protection following immunisation is diminished. Additional immunisation of direct contacts and in particular healthcare workers (HCWs) has proven added value. As vaccination coverage in HCWs remains low, we aimed to gain insight in the factors behind the demotivation for influenza vaccination.

METHODS

Attitudes and believes towards influenza vaccination and socio-demographic and professional determinants were surveyed in 5141 Belgian HCWs from 13 hospitals and 14 nursing homes. Additionally, influenza campaign coordinators of the participating healthcare institutions were interviewed about the factors of success/failure in their campaigns.

RESULTS

The mean vaccination coverage registered by the participating healthcare institutions was 40.4% in the hospitals and 45.3% in the nursing homes. Overall, up to 90% of HCWs found it important not to infect their patients. However, only 20% of non-vaccinated HCWs considered influenza vaccination a duty to not harm their patients. Up to 40% of unvaccinated staff believed they could get influenza after vaccination and that vaccination weakens their immune system. Also, only about 20% of unvaccinated staff thought to have a high chance of getting influenza. Reasons for unvaccinated staff to get vaccinated in the future are self-protection and protection of family members. Factors that positively influenced vaccination coverage are encouragement by supervisors (OR, hospitals: 7.1, p < 0.001; nursing homes: 7.5, p < 0.001) and well-organized vaccination campaigns with on-site vaccination. Factors that negatively affected vaccination coverage are misconceptions about influenza and its vaccine (OR, range 0.1-0.7, p < 0.001 for most misconceptions) and underestimation of the risk of contracting influenza by patients or HCWs (OR of perceived susceptibility, range 2.1-5.1, p < 0.001 for most factors).

CONCLUSION

There is a need for guidance for the organization of seasonal influenza campaigns, in which education, communication and easy accessible vaccination are promoted.

Estimating influenza vaccine effectiveness: Evolution of methods to better understand effects of confounding in older adults

Older adults are at high risk for serious complications of influenza illness and loss of vaccine-mediated protection. It is increasingly recognized that in addition to age, multiple chronic conditions and associated frailty contribute to the decline in vaccine effectiveness in this population. However, observational studies have been fraught with issues of confounding related to the degree of frailty and functional decline, measures of which are not included in standard administrative health care databases that are used to calculate vaccine effectiveness. This issue has led to the identification of confounding by indication or from "healthy vaccinee" bias, which respectively lead to underestimates or overestimates of influenza vaccine effectiveness. In addition, the sensitivity and specificity of the criteria used to define influenza-like illness declines with increasing age due to atypical presentations of illness and the inability to distinguish between influenza and other respiratory viruses. The test-negative case:control design has emerged as a method to estimate influenza vaccine effectiveness by comparing vaccination rates in those with laboratory-confirmed influenza to those with other acute viral respiratory illnesses. This review provides a perspective on how test-negative case:control study designs and new insights into mechanisms of protection have considerably strengthened influenza vaccination policy decisions for older adults that have historically been undermined by the conclusions of observational studies.