The Unexpected Impact of Vaccines on Secondary Bacterial Infections Following Influenza

Invasive Pneumococcal Disease Epidemiology and Serotype Replacement After the Introduction of the 13-Valent Pneumococcal Conjugate Vaccine in Ontario, Canada, 2007-2022

Background

New vaccine products were recently authorized for protection against invasive pneumococcal disease (IPD) in Canada. Our aim was to determine age- and serotype-specific trends in IPD incidence and severity in Canada's largest province, Ontario.

Methods

We included all confirmed IPD cases reported in Ontario and defined the pre-pneumococcal 13-valent conjugate vaccine (PCV13) era (01/2007 to 12/2010), post-PCV13 era (01/2011 to 12/2019), and coronavirus disease 2019 (COVID-19) pandemic era (01/2020 to 12/2022). We estimated incidence, hospitalization, and case fatality rate (CFR) by age. We grouped IPD cases by vaccine-specific serotypes (PCV13; PCV15-non-PCV13; PCV20-non-PCV13; PCV20-non-PCV15; polysaccharide 23-valent vaccine-non-PCV20; and non-vaccine-preventable [NVP]). We then compared incidence rates by age and serotype group in the pre- and post-PCV13 eras by calculating rate ratios (RRs) and their 95% CIs.

Results

Incidence and hospitalizations declined from the pre- to post-PCV13 era in children aged <5 years (RR, 0.7; 95% CI, 0.6-0.8; and RR, 0.8; 95% CI, 0.7-0.9, respectively), but the CFR increased (1.4% to 2.3%). Other age groups saw smaller declines or more stable incidence rates across the years; hospitalizations increased in adults aged 50-64 years (RR, 1.2; 95% CI, 1.1-1.4) and ≥65 years (RR, 1.1; 95% CI, 1.0-1.1). For all ages, IPD cases and hospitalizations attributable to PCV13 serotypes declined, and those attributable to PCV15-non-PCV13, PCV20-non-PCV13, and NVP serotypes increased. IPD incidence declined during the COVID-19 era.

Conclusions

IPD incidence and hospitalizations due to PCV13 serotypes decreased after PCV13 introduction but increased for other serotypes. Continued surveillance is required to evaluate changes to pneumococcal vaccination programs and ongoing changes to the distribution of IPD-causing serotypes.

Vaccines Induce Homeostatic Immunity, Generating Several Secondary Benefits

The optimal immune response eliminates invading pathogens, restoring immune equilibrium without inflicting undue harm to the host. However, when a cascade of immunological reactions is triggered, the immune response can sometimes go into overdrive, potentially leading to harmful long-term effects or even death. The immune system is triggered mostly by infections, allergens, or medical interventions such as vaccination. This review examines how these immune triggers differ and why certain infections may dysregulate immune homeostasis, leading to inflammatory or allergic pathology and exacerbation of pre-existing conditions. However, many vaccines generate an optimal immune response and protect against the consequences of pathogen-induced immunological aggressiveness, and from a small number of unrelated pathogens and autoimmune diseases. Here, we propose an "immuno-wave" model describing a vaccine-induced "Goldilocks immunity", which leaves fine imprints of both pro-inflammatory and anti-inflammatory milieus, derived from both the innate and the adaptive arms of the immune system, in the body. The resulting balanced, 'quiet alert' state of the immune system may provide a jump-start in the defense against pathogens and any associated pathological inflammatory or allergic responses, allowing vaccines to go above and beyond their call of duty. In closing, we recommend formally investigating and reaping many of the secondary benefits of vaccines with appropriate clinical studies.

A conserved antigen induces respiratory Th17-mediated broad serotype protection against pneumococcal superinfection

Several vaccines targeting bacterial pathogens show reduced efficacy upon concurrent viral infection, indicating that a new vaccinology approach is required. To identify antigens for the human pathogen Streptococcus pneumoniae that are effective following influenza infection, we performed CRISPRi-seq in a murine model of superinfection and identified the conserved lafB gene as crucial for virulence. We show that LafB is a membrane-associated, intracellular protein that catalyzes the formation of galactosyl-glucosyl-diacylglycerol, a glycolipid important for cell wall homeostasis. Respiratory vaccination with recombinant LafB, in contrast to subcutaneous vaccination, was highly protective against S. pneumoniae serotypes 2, 15A, and 24F in a murine model. In contrast to standard capsule-based vaccines, protection did not require LafB-specific antibodies but was dependent on airway CD4+ T helper 17 cells. Healthy human individuals can elicit LafB-specific immune responses, indicating LafB antigenicity in humans. Collectively, these findings present a universal pneumococcal vaccine antigen that remains effective following influenza infection.

Old and new aspects of influenza

Influenza is a classic infectious disease that, through the continuous variation of the viruses that produce it, imposes new challenges that we must solve as quickly as possible. The COVID-19 pandemic has substantially modified the behavior of influenza and other respiratory viruses, and in the coming years we will have to coexist with a new pathogen that will probably interact with existing pathogens in a way that we cannot yet glimpse. However, knowledge prior to the pandemic allows us to focus on the aspects that must be modified to make influenza an acceptable challenge for the future. In this review, emphasis is placed on the most relevant aspects of epidemiology, disease burden, diagnosis, and vaccine prevention, and how scientific and clinical trends in these aspects flow from the previously known to future challenges.

Memory Th17 cell-mediated protection against lethal secondary pneumococcal pneumonia following influenza infection

Streptococcus pneumoniae (Sp) frequently causes secondary pneumonia after influenza A virus (IAV) infection, leading to high morbidity and mortality worldwide. Concomitant pneumococcal and influenza vaccination improves protection against coinfection but does not always yield complete protection. Impaired innate and adaptive immune responses have been associated with attenuated bacterial clearance in influenza virus-infected hosts. In this study, we showed that preceding low-dose IAV infection caused persistent Sp infection and suppression of bacteria-specific T-helper type 17 (Th17) responses in mice. Prior Sp infection protected against subsequent IAV/Sp coinfection by improving bacterial clearance and rescuing bacteria-specific Th17 responses in the lungs. Furthermore, blockade of IL-17A by anti-IL-17A antibodies abrogated the protective effect of Sp preinfection. Importantly, memory Th17 responses induced by Sp preinfection overcame viral-driven Th17 inhibition and provided cross-protection against different Sp serotypes following coinfection with IAV. These results indicate that bacteria-specific Th17 memory cells play a key role in providing protection against IAV/Sp coinfection in a serotype-independent manner and suggest that a Th17-based vaccine would have excellent potential to mitigate disease caused by coinfection. IMPORTANCE Streptococcus pneumoniae (Sp) frequently causes secondary bacterial pneumonia after influenza A virus (IAV) infection, leading to increased morbidity and mortality worldwide. Current pneumococcal vaccines induce highly strain-specific antibody responses and provide limited protection against IAV/Sp coinfection. Th17 responses are broadly protective against Sp single infection, but whether the Th17 response, which is dramatically impaired by IAV infection in naïve mice, might be effective in immunization-induced protection against pneumonia caused by coinfection is not known. In this study, we have revealed that Sp-specific memory Th17 cells rescue IAV-driven inhibition and provide cross-protection against subsequent lethal coinfection with IAV and different Sp serotypes. These results indicate that a Th17-based vaccine would have excellent potential to mitigate disease caused by IAV/Sp coinfection.

Real-World Evidence in Cost-Effectiveness Analysis of Enhanced Influenza Vaccines in Adults ≥ 65 Years of Age: Literature Review and Expert Opinion

Influenza vaccination can benefit most populations, including adults ≥ 65 years of age, who are at greater risk of influenza-related complications. In many countries, enhanced vaccines, such as adjuvanted, high-dose, and recombinant trivalent/quadrivalent influenza vaccines (aTIV/aQIV, HD-TIV/HD-QIV, and QIVr, respectively), are recommended in older populations to provide higher immunogenicity and increased relative vaccine efficacy/effectiveness (rVE) than standard-dose vaccines. This review explores how efficacy and effectiveness data from randomized controlled trials and real-world evidence (RWE) are used in economic evaluations. Findings from published cost-effectiveness analyses (CEA) on enhanced influenza vaccines for older adults are summarized, and the assumptions and approaches used in these CEA are assessed alongside discussion of the importance of RWE in CEA. Results from many CEA showed that adjuvanted and high-dose enhanced vaccines were cost-effective compared with standard vaccines, and that differences in rVE estimates and acquisition price may drive differences in cost-effectiveness estimates between enhanced vaccines. Overall, RWE and CEA provide clinical and economic rationale for enhanced vaccine use in people ≥ 65 years of age, an at-risk population with substantial burden of disease. Countries that consider RWE when making vaccine recommendations have preferentially recommended aTIV/aQIV, as well as HD-TIV/HD-QIV and QIVr, to protect older individuals.

Antigen-specific memory Th17 cells promote cross-protection against nontypeable Haemophilus influenzae after mild influenza A virus infection

Secondary bacterial pneumonia after influenza A virus (IAV) infection is the leading cause of hospitalization and death associated with IAV infection worldwide. Nontypeable Haemophilus influenzae (NTHi) is one of the most common causes of secondary bacterial pneumonia. Current efforts to develop vaccines against NTHi infection focus on inducing antibodies but are hindered by antigenic diversity among NTHi strains. Therefore, we investigated the contribution of the memory T helper type 17 (Th17) response in protective immunity against IAV/NTHi coinfection. We observed that even a mild IAV infection impaired the NTHi-specific Th17 response and increased morbidity and mortality compared with NTHi monoinfected mice. However, pre-existing memory NTHi-specific Th17 cells induced by a previous NTHi infection overcame IAV-driven Th17 inhibition and were cross-protective against different NTHi strains. Last, mice immunized with a NTHi protein that induced a strong Th17 memory response were broadly protected against diverse NTHi strains after challenge with coinfection. These results indicate that vaccination that limits IAV infection to mild disease may be insufficient to eliminate the risk of a lethal secondary bacterial pneumonia. However, NTHi-specific memory Th17 cells provide serotype-independent protection despite an ongoing IAV infection and demonstrate the advantage of developing broadly protective Th17-inducing vaccines against secondary bacterial pneumonia.

Global mortality associated with 33 bacterial pathogens in 2019: a systematic analysis for the Global Burden of Disease Study 2019

BACKGROUND

Reducing the burden of death due to infection is an urgent global public health priority. Previous studies have estimated the number of deaths associated with drug-resistant infections and sepsis and found that infections remain a leading cause of death globally. Understanding the global burden of common bacterial pathogens (both susceptible and resistant to antimicrobials) is essential to identify the greatest threats to public health. To our knowledge, this is the first study to present global comprehensive estimates of deaths associated with 33 bacterial pathogens across 11 major infectious syndromes.

METHODS

We estimated deaths associated with 33 bacterial genera or species across 11 infectious syndromes in 2019 using methods from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, in addition to a subset of the input data described in the Global Burden of Antimicrobial Resistance 2019 study. This study included 343 million individual records or isolates covering 11 361 study-location-years. We used three modelling steps to estimate the number of deaths associated with each pathogen: deaths in which infection had a role, the fraction of deaths due to infection that are attributable to a given infectious syndrome, and the fraction of deaths due to an infectious syndrome that are attributable to a given pathogen. Estimates were produced for all ages and for males and females across 204 countries and territories in 2019. 95% uncertainty intervals (UIs) were calculated for final estimates of deaths and infections associated with the 33 bacterial pathogens following standard GBD methods by taking the 2·5th and 97·5th percentiles across 1000 posterior draws for each quantity of interest.

FINDINGS

From an estimated 13·7 million (95% UI 10·9-17·1) infection-related deaths in 2019, there were 7·7 million deaths (5·7-10·2) associated with the 33 bacterial pathogens (both resistant and susceptible to antimicrobials) across the 11 infectious syndromes estimated in this study. We estimated deaths associated with the 33 bacterial pathogens to comprise 13·6% (10·2-18·1) of all global deaths and 56·2% (52·1-60·1) of all sepsis-related deaths in 2019. Five leading pathogens-Staphylococcus aureus, Escherichia coli, Streptococcus pneumoniae, Klebsiella pneumoniae, and Pseudomonas aeruginosa-were responsible for 54·9% (52·9-56·9) of deaths among the investigated bacteria. The deadliest infectious syndromes and pathogens varied by location and age. The age-standardised mortality rate associated with these bacterial pathogens was highest in the sub-Saharan Africa super-region, with 230 deaths (185-285) per 100 000 population, and lowest in the high-income super-region, with 52·2 deaths (37·4-71·5) per 100 000 population. S aureus was the leading bacterial cause of death in 135 countries and was also associated with the most deaths in individuals older than 15 years, globally. Among children younger than 5 years, S pneumoniae was the pathogen associated with the most deaths. In 2019, more than 6 million deaths occurred as a result of three bacterial infectious syndromes, with lower respiratory infections and bloodstream infections each causing more than 2 million deaths and peritoneal and intra-abdominal infections causing more than 1 million deaths.

INTERPRETATION

The 33 bacterial pathogens that we investigated in this study are a substantial source of health loss globally, with considerable variation in their distribution across infectious syndromes and locations. Compared with GBD Level 3 underlying causes of death, deaths associated with these bacteria would rank as the second leading cause of death globally in 2019; hence, they should be considered an urgent priority for intervention within the global health community. Strategies to address the burden of bacterial infections include infection prevention, optimised use of antibiotics, improved capacity for microbiological analysis, vaccine development, and improved and more pervasive use of available vaccines. These estimates can be used to help set priorities for vaccine need, demand, and development.

FUNDING

Bill & Melinda Gates Foundation, Wellcome Trust, and Department of Health and Social Care, using UK aid funding managed by the Fleming Fund.

Prior influenza vaccine is not a risk factor for bacterial coinfection in patients admitted to the ICU due to severe influenza

OBJECTIVE

To determine whether the prior usage of the flu vaccine is a risk factor for bacterial co-infection in patients with severe influenza.

DESIGN

This was a retrospective observational cohort study of subjects admitted to the ICU. A propensity score matching, and logistic regression adjusted for potential confounders were carried out to evaluate the association between prior influenza vaccination and bacterial co-infection.

SETTINGS

184 ICUs in Spain due to severe influenza.

PATIENTS

Patients included in the Spanish prospective flu registry.

INTERVENTIONS

Flu vaccine prior to the hospital admission.

RESULTS

A total of 4175 subjects were included in the study. 489 (11.7%) received the flu vaccine prior to develop influenza infection. Prior vaccinated patients were older 71 [61-78], and predominantly male 65.4%, with at least one comorbid condition 88.5%. Prior vaccination was not associated with bacterial co-infection in the logistic regression model (OR: 1.017; 95%CI 0.803-1.288; p=0.885). After matching, the average treatment effect of prior influenza vaccine on bacterial co-infection was not statistically significant when assessed by propensity score matching (p=0.87), nearest neighbor matching (p=0.59) and inverse probability weighting (p=0.99).

CONCLUSIONS

No association was identified between prior influenza vaccine and bacterial coinfection in patients admitted to the ICU due to severe influenza. Post influenza vaccination studies are necessary to continue evaluating the possible benefits.

Time-Dependent Increase in Susceptibility and Severity of Secondary Bacterial Infections During SARS-CoV-2

Secondary bacterial infections can exacerbate SARS-CoV-2 infection, but their prevalence and impact remain poorly understood. Here, we established that a mild to moderate infection with the SARS-CoV-2 USA-WA1/2020 strain increased the risk of pneumococcal (type 2 strain D39) coinfection in a time-dependent, but sex-independent, manner in the transgenic K18-hACE2 mouse model of COVID-19. Bacterial coinfection increased lethality when the bacteria was initiated at 5 or 7 d post-virus infection (pvi) but not at 3 d pvi. Bacterial outgrowth was accompanied by neutrophilia in the groups coinfected at 7 d pvi and reductions in B cells, T cells, IL-6, IL-15, IL-18, and LIF were present in groups coinfected at 5 d pvi. However, viral burden, lung pathology, cytokines, chemokines, and immune cell activation were largely unchanged after bacterial coinfection. Examining surviving animals more than a week after infection resolution suggested that immune cell activation remained high and was exacerbated in the lungs of coinfected animals compared with SARS-CoV-2 infection alone. These data suggest that SARS-CoV-2 increases susceptibility and pathogenicity to bacterial coinfection, and further studies are needed to understand and combat disease associated with bacterial pneumonia in COVID-19 patients.

Don't Let It Get Under Your Skin! - Vaccination Protects the Skin Barrier of Common Carp From Disruption Caused by Cyprinid Herpesvirus 3

Vaccination is the best form of protecting fish against viral diseases when the pathogen cannot be contained by biosecurity measures. Vaccines based on live attenuated viruses seem to be most effective for vaccination against challenging pathogens like Cyprinid herpesvirus 3. However, there are still knowledge gaps how these vaccines effectively protect fish from the deadly disease caused by the epitheliotropic CyHV-3, and which aspects of non-direct protection of skin or gill integrity and function are important in the aquatic environment. To elucidate some elements of protection, common carp were vaccinated against CyHV-3 using a double deletion vaccine virus KHV-T ΔDUT/TK in the absence or presence of a mix of common carp beta-defensins 1, 2 and 3 as adjuvants. Vaccination induced marginal clinical signs, low virus load and a minor upregulation of cd4, cd8 and igm gene expression in vaccinated fish, while neutralisation activity of blood serum rose from 14 days post vaccination (dpv). A challenge infection with CyHV-3 induced a severe disease with 80-100% mortality in non-vaccinated carp, while in vaccinated carp, no mortality was recorded and the virus load was >1,000-fold lower in the skin, gill and kidney. Histological analysis showed strongest pathological changes in the skin, with a complete destruction of the epidermis in non-vaccinated carp. In the skin of non-vaccinated fish, T and B cell responses were severely downregulated, inflammation and stress responses were increased upon challenge, whereas vaccinated fish had boosted neutrophil, T and B cell responses. A disruption of skin barrier elements (tight and adherence junction, desmosomes, mucins) led to an uncontrolled increase in skin bacteria load which most likely exacerbated the inflammation and the pathology. Using a live attenuated virus vaccine, we were able to show that increased neutrophil, T and B cell responses provide protection from CyHV-3 infection and lead to preservation of skin integrity, which supports successful protection against additional pathogens in the aquatic environment which foster disease development in non-vaccinated carp.

Antibiotic Resistance Patterns and Association with the Influenza Season in the United States: A Multicenter Evaluation Reveals Surprising Associations Between Influenza Season and Resistance in Gram-negative Pathogens

Background

Viral infections are often treated with empiric antibiotics due to suspected bacterial coinfections, leading to antibiotic overuse. We aimed to describe antibiotic resistance (ABR) trends and their association with the influenza season in ambulatory and inpatient settings in the United States.

Methods

We used the BD Insights Research Database to evaluate antibiotic susceptibility profiles in 30-day nonduplicate bacterial isolates collected from patients >17 years old at 257 US healthcare institutions from 2011 to 2019. We investigated ABR in Gram-positive (Staphylococcus aureus and Streptococcus pneumoniae) and Gram-negative (Enterobacterales [ENT], Pseudomonas aeruginosa [PSA], and Acinetobacter baumannii spp [ACB]) bacteria expressed as the proportion of isolates not susceptible ([NS], intermediate or resistant) and resistance per 100 admissions (inpatients only). Antibiotics included carbapenems (Carb), fluoroquinolones (FQ), macrolides, penicillin, extended-spectrum cephalosporins (ESC), and methicillin. Generalized estimating equations models were used to evaluate monthly trends in ABR outcomes and associations with community influenza rates.

Results

We identified 8 250 860 nonduplicate pathogens, including 154 841 Gram-negative Carb-NS, 1 502 796 Gram-negative FQ-NS, 498 012 methicillin-resistant S aureus (MRSA), and 44 131 NS S pneumoniae. All S pneumoniae rates per 100 admissions (macrolide-, penicillin-, and ESC-NS) were associated with influenza rates. Respiratory, but not nonrespiratory, MRSA was also associated with influenza. For Gram-negative pathogens, influenza rates were associated with the percentage of FQ-NS ENT, FQ-NS PSA, and Carb-NS ACB.

Conclusions

Our study showed expected increases in rates of ABR Gram-positive and identified small but surprising increases in ABR Gram-negative pathogens associated with influenza activity. These insights may help inform antimicrobial stewardship initiatives.

Utilization of drugs with reports on potential efficacy or harm on COVID-19 before, during, and after the first pandemic wave

PURPOSE

Conflicting information on potential benefits of drugs as well as reports on hypothetical harm of commonly used drugs in COVID-19 treatment have challenged clinicians and healthcare systems. We analyzed the change in ambulatory drug utilization before, during, and after the first wave of the pandemic in 2020.

METHODS

We explored dispensing data of nearly 19 000 pharmacies at the expense of the statutory health insurance funds covering 88% of Germany's population. We analyzed utilization of publicly discussed drugs with conflicting information. Drug utilization as number of packages dispensed per week from January to June 2020, reflecting 314 million claims, was compared with 2019.

RESULTS

Utilization of hydroxychloroquine increased +110% during March 2020 and then slightly decreased until week April 13-19. Renin-angiotensin-aldosterone system inhibitors and simvastatin/atorvastatin increased, +78% and +74%, respectively, and subsequently decreased below 2019 levels. Utilization of azithromycin and all systemic antibiotics decreased continuously from March 2-8 until June to levels considerably lower compared to 2019 (June 22-28: azithromycin: -55%, all systemic antibiotics: -27%). Pneumococcal vaccines utilization initially increased +373%, followed by supply shortages. Paracetamol utilization showed an initial increase of +111%, mainly caused by an increase of over-the-counter dispensings.

CONCLUSIONS

Apart from the pandemic itself, the data suggest that dissemination of misinformation and unsound speculations as well as supply shortages influenced drug prescribing, utilization, and purchasing behavior. The findings can inform post-pandemic policy to prevent unfounded over- and underprescribing and off-label use as well as drug shortages during a public health crisis.

Prior influenza vaccine is not a risk factor for bacterial coinfection in patients admitted to the ICU due to severe influenza

OBJECTIVE

To determine whether the prior usage of the flu vaccine is a risk factor for bacterial co-infection in patients with severe influenza.

DESIGN

This was a retrospective observational cohort study of subjects admitted to the ICU. A propensity score matching, and logistic regression adjusted for potential confounders were carried out to evaluate the association between prior influenza vaccination and bacterial co-infection.

SETTINGS

184 ICUs in Spain due to severe influenza.

PATIENTS

Patients included in the Spanish prospective flu registry.

INTERVENTIONS

Flu vaccine prior to the hospital admission.

RESULTS

A total of 4175 subjects were included in the study. 489 (11.7%) received the flu vaccine prior to develop influenza infection. Prior vaccinated patients were older 71 [61-78], and predominantly male 65.4%, with at least one comorbid condition 88.5%. Prior vaccination was not associated with bacterial co-infection in the logistic regression model (OR: 1.017; 95%CI 0.803-1.288; p=0.885). After matching, the average treatment effect of prior influenza vaccine on bacterial co-infection was not statistically significant when assessed by propensity score matching (p=0.87), nearest neighbor matching (p=0.59) and inverse probability weighting (p=0.99).

CONCLUSIONS

No association was identified between prior influenza vaccine and bacterial coinfection in patients admitted to the ICU due to severe influenza. Post influenza vaccination studies are necessary to continue evaluating the possible benefits.

Flu Virus Attenuates Memory Clearance of Pneumococcus via IFN-γ-Dependent Th17 and Independent Antibody Mechanisms

Bacterial coinfection is a major cause of influenza-associated mortality. Most people have experienced infections with bacterial pathogens commonly associated with influenza A virus (IAV) coinfection before IAV exposure; however, bacterial clearance through the immunological memory response (IMR) in coinfected patients is inefficient, suggesting that the IMR to bacteria is impaired during IAV infection. Adoptive transfer of CD4⁺ T cells from mice that had experienced bacterial infection into IAV-infected mice revealed that memory protection against bacteria was weakened in the latter. Additionally, memory Th17 cell responses were impaired due to an IFN-γ-dependent reduction in Th17 cell proliferation and delayed migration of CD4⁺ T cells into the lungs. A bacterium-specific antibody-mediated memory response was also substantially reduced in coinfected mice, independently of IFN-γ. These findings provide additional perspectives on the pathogenesis of coinfection and suggest additional strategies for the treatment of defective antibacterial immunity and the design of bacterial vaccines against coinfection.

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Memory protection against bacteria was impaired in coinfection

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Memory Th17 response to bacteria was reduced by IAV-induced IFN-γ

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The Th17 reduction was caused by impeded Th17 proliferation and migration

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Bacteria-specific antibody was reduced in coinfection independent of IFN-γ

The Association between Influenza and Pneumococcal Vaccinations and SARS-Cov-2 Infection: Data from the EPICOVID19 Web-Based Survey

The present study aims to evaluate whether influenza and pneumococcal vaccinations are associated with positive nasopharyngeal swab (NPS) testing to detect SARS-CoV-2. Data from the Italian cross-sectional web-based survey (EPICOVID19), based on a self-selection sample of individuals aged ≥18, were considered. The probability of a positive SARS-CoV-2 NPS test result as a function of influenza or anti-pneumococcal vaccination was evaluated using multivariable logistic regression, stratifying analysis by age (<65 years, ≥65 years). From April 2020, 170,731 individuals aged <65 years and 28,097 ≥65 years filled out the EPICOVID19 questionnaire. Influenza and anti-pneumococcal vaccinations were received, respectively, by 16% and 2% of those <65 years, and by 53% and 13% of those ≥65 years. SARS-CoV-2 NPS testing was reported by 6680 participants. Anti-pneumococcal and influenza vaccinations were associated with a decreased probability of a SARS-CoV-2 NPS positive test in the younger participants (OR = 0.61, 95% CI 0.41-0.91; OR = 0.85, 95%CI 0.74-0.98; respectively). A significantly lower probability of a positive test result was detected in the individuals ≥65 years who received anti-pneumococcal vaccination (OR = 0.56, 95%CI 0.33-0.95). These results need to be confirmed by further investigations, but they are relevant given the probable coexistence of influenza, bacterial infections, and COVID-19 over the coming autumn-winter season.

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.

Risk Factors for Influenza Virus Related Severe Lower Respiratory Tract Infection in Children

BACKGROUND

Influenza virus is one of the most common respiratory pathogens for all age groups and may cause seasonal outbreaks. Our aim was to identify risk groups and factors associated with severe clinical course including mortality in children with influenza-related lower respiratory tract infection (LRTI).

METHODS

We conducted a retrospective study in children hospitalized with influenza virus LRTI from 2008 to 2018. Data on demographic features, influenza type, viral coinfection, primary and secondary bacterial infections (SBIs), time of onset of antiviral treatment, comorbidities, hospitalization length, pediatric intensive care unit admission/invasive mechanical ventilation (IMV) need and mortality were collected from medical records.

RESULTS

There were 280 patients hospitalized with LRTI and median hospitalization length was 9 days. Congenital heart disease, neuromuscular disease, SBIs and late-onset antiviral treatment were independent risk factors for prolonged hospital stay (P < 0.05). Pediatric intensive care unit admission was present in 20.4% (57) of the patients and 17.1% (48) of all patients required IMV. SBIs, lymphopenia, neutrophilia, immunosuppression and human bocavirus coinfection were independent risk factors for IMV support (P < 0.05). Eighteen patients died and immunosuppression, lymphopenia and SBIs were independent risk factors for mortality (P < 0.05).

CONCLUSIONS

Presence of comorbidity, SBIs, neutrophilia and lymphopenia at admission identified as risk factors for severe influenza infections including need for IMV and death. Although several studies showed that antiviral treatment reduce hospitalization, complications and mortality, there is a lack of prospective trials and patients for antiviral therapy should be carefully chosen by the clinician.

A Novel Role for PDZ-Binding Motif of Influenza A Virus Nonstructural Protein 1 in Regulation of Host Susceptibility to Postinfluenza Bacterial Superinfections

Influenza A viruses (IAVs) have multiple mechanisms for altering the host immune response to aid in virus survival and propagation. While both type I and II interferons (IFNs) have been associated with increased bacterial superinfection (BSI) susceptibility, we found that in some cases type I IFNs can be beneficial for BSI outcome. Specifically, we have shown that antagonism of the type I IFN response during infection by some IAVs can lead to the development of deadly BSI. The nonstructural protein 1 (NS1) from IAV is well known for manipulating host type I IFN responses, but the viral proteins mediating BSI severity remain unknown. In this study, we demonstrate that the PDZ-binding motif (PDZ-bm) of the NS1 C-terminal region from mouse-adapted A/Puerto Rico/8/34-H1N1 (PR8) IAV dictates BSI susceptibility through regulation of IFN-α/β production. Deletion of the NS1 PDZ-bm from PR8 IAV (PR8-TRUNC) resulted in 100% survival and decreased bacterial burden in superinfected mice compared with 0% survival in mice superinfected after PR8 infection. This reduction in BSI susceptibility after infection with PR8-TRUNC was due to the presence of IFN-β, as protection from BSI was lost in Ifn-β^-/- mice, resembling BSI during PR8 infection. PDZ-bm in PR8-infected mice inhibited the production of IFN-β posttranscriptionally, and both delayed and reduced expression of the tunable interferon-stimulated genes. Finally, a similar lack of BSI susceptibility, due to the presence of IFN-β on day 7 post-IAV infection, was also observed after infection of mice with A/TX98-H3N2 virus that naturally lacks a PDZ-bm in NS1, indicating that this mechanism of BSI regulation by NS1 PDZ-bm may not be restricted to PR8 IAV. These results demonstrate that the NS1 C-terminal PDZ-bm, like the one present in PR8 IAV, is involved in controlling susceptibility to BSI through the regulation of IFN-β, providing new mechanisms for NS1-mediated manipulation of host immunity and BSI severity.

Influenza and the Surgeon

BACKGROUND

The influenza virus is a pathogenic virus responsible for large numbers of deaths and long-term disabilities worldwide. Although the very young, the very old, and immunocompromised individuals are most susceptible, the effects of the influenza virus can be observed across the entire spectrum of individuals.

DISCUSSION

Infection with the influenza virus induces a substantial inflammatory and immunologic response and induces marked pulmonary inflammation. Many aspects of influenza affect surgical patients directly. Vaccines are one of the most effective measures aimed at reducing the prevalence and severity of many infectious diseases, including the influenza virus. Vaccination programs remain one of the highest priorities across the spectrum of countries, research institutions such as the National Institutes of Health, international health agencies such as the World Health Organization (WHO), and major non-profit organizations.

CONCLUSION

This review addresses aspects of the immune and inflammatory response to influenza, with a focus on the elderly population and healthcare providers who may act as reservoirs for virus transmission to the vulnerable surgical population.

[Some thoughts on influenza vaccine and regular influenza vaccination for healthcare workers]

It has been 100 years since the 1918 influenza pandemic but influenza is still an uncontrolled infectious disease. In some developed countries, the coverage rate of influenza vaccine can reach as high as 60%-70%, and even up to 90% or higher in some specific population, such as the elderly and healthcare workers. The coverage rate of influenza vaccination in Chinese people, however, is very low, only about 2%-3% per year. The limitations of influenza vaccine, and the purpose and significance of influenza vaccination, the imbalance of vaccine information and the importance of inoculation for healthcare workers are discussed in this paper. The resistance to popularize influenza vaccination is explored from different perspectives. It is hoped that more people will recognize the objective epidemiological data, and get rid of misunderstandings based on their experiences. Healthcare workers in particular, and the general population, should be encouraged to have an influenza vaccination.

[Some thoughts on influenza vaccine and regular influenza vaccination for healthcare workers]

It has been 100 years since the 1918 influenza pandemic but influenza is still an uncontrolled infectious disease. In some developed countries, the coverage rate of influenza vaccine can reach as high as 60%-70%, and even up to 90% or higher in some specific population, such as the elderly and healthcare workers. The coverage rate of influenza vaccination in Chinese people, however, is very low, only about 2%-3% per year. The limitations of influenza vaccine, and the purpose and significance of influenza vaccination, the imbalance of vaccine information and the importance of inoculation for healthcare workers are discussed in this paper. The resistance to popularize influenza vaccination is explored from different perspectives. It is hoped that more people will recognize the objective epidemiological data, and get rid of misunderstandings based on their experiences. Healthcare workers in particular, and the general population, should be encouraged to have an influenza vaccination.

Validated Models of Immune Response to Virus Infection

Viruses are a main cause of disease worldwide and many are without effective therapeutics or vaccines. A lack of understanding about how host responses work to control viral spread is one factor limiting effective management. How different immune components regulate infection dynamics is beginning to be better understood with the help of mathematical models. These models have been key in discriminating between hypotheses and in identifying rates of virus growth and clearance, dynamical control by different host factors and antivirals, and synergistic interactions during multi-pathogen infections. A recent focus in evaluating model predictions in the laboratory and clinic has illuminate the accuracy of models for a variety of viruses and highlighted the critical nature of theoretical approaches in virology. Here, I discuss recent model-driven exploration of host-pathogen interactions that have illustrated the importance of model validation in establishing the model's predictive capability and in defining new biology.

Host-pathogen kinetics during influenza infection and coinfection: insights from predictive modeling

Influenza virus infections are a leading cause of morbidity and mortality worldwide. This is due in part to the continual emergence of new viral variants and to synergistic interactions with other viruses and bacteria. There is a lack of understanding about how host responses work to control the infection and how other pathogens capitalize on the altered immune state. The complexity of multi-pathogen infections makes dissecting contributing mechanisms, which may be non-linear and occur on different time scales, challenging. Fortunately, mathematical models have been able to uncover infection control mechanisms, establish regulatory feedbacks, connect mechanisms across time scales, and determine the processes that dictate different disease outcomes. These models have tested existing hypotheses and generated new hypotheses, some of which have been subsequently tested and validated in the laboratory. They have been particularly a key in studying influenza-bacteria coinfections and will be undoubtedly be useful in examining the interplay between influenza virus and other viruses. Here, I review recent advances in modeling influenza-related infections, the novel biological insight that has been gained through modeling, the importance of model-driven experimental design, and future directions of the field.

Intermediate levels of vaccination coverage may minimize seasonal influenza outbreaks

For most pathogens, vaccination reduces the spread of the infection and total number of cases; thus, public policy usually advocates maximizing vaccination coverage. We use simple mathematical models to explore how this may be different for pathogens, such as influenza, which exhibit strain variation. Our models predict that the total number of seasonal influenza infections is minimized at an intermediate (rather than maximal) level of vaccination, and, somewhat counter-intuitively, further increasing the level of the vaccination coverage may lead to higher number of influenza infections and be detrimental to the public interest. This arises due to the combined effects of: competition between multiple co-circulating strains; limited breadth of protection afforded by the vaccine; and short-term strain-transcending immunity following natural infection. The study highlights the need for better quantification of the components of vaccine efficacy and longevity of strain-transcending cross-immunity in order to generate nuanced recommendations for influenza vaccine coverage levels.