The substantial hospitalization burden of influenza in central China: surveillance for severe, acute respiratory infection, and influenza viruses, 2010-2012

Transplacental transfer efficiency of maternal antibodies against influenza A(H1N1)pdm09 virus and dynamics of naturally acquired antibodies in Chinese children: a longitudinal, paired mother-neonate cohort study

BACKGROUND

The 2009 pandemic H1N1 influenza A virus (A(H1N1)pdm09 virus) evolves rapidly and has continued to cause severe infections in children since its emergence in 2009. We aimed to characterise the kinetics of maternally and naturally acquired antibodies against historical A(H1N1)pdm09 strains and to assess the extent to which the response to heterologous strains following infection or vaccination affects observed A(H1N1)pdm09 strain-specific antibody titres in a Chinese paediatric population.

METHODS

In this retrospective study, we used residual serum samples from 528 mother-neonate pairs from a non-interventional, longitudinal cohort study in southern China conducted from Sept 20, 2013, to Aug 24, 2018, from six local hospitals in Anhua County, Hunan Province, China. Mother-neonate pairs were eligible for inclusion if the neonates were born after Sept 20, 2013, and their mothers had resided in the study sites for at least 3 months. We tested samples with a haemagglutination inhibition (HAI) assay to measure antibody levels against three historical A(H1N1)pdm09 strains that were antigenically similar to the strains that circulated during the 2009 pandemic (A/Hunan-Kaifu/SWL4204/2009 [SWL4204/09 strain], A/Hunan-Daxiang/SWL1277/2016 [SWL1277/16 strain], and A/Hunan-Yanfeng/SWL185/2018 [SWL185/18 strain]). We also determined the seroprevalence, geometric mean titres (GMTs), transfer ratio of maternal antibodies, and the dynamics of maternally and naturally acquired antibodies in children, from birth to 3 years of age.

FINDINGS

1066 mother-neonate pairs were enrolled in the original cohort between Sept 20, 2013, and Oct 14, 2015. Of these, 528 pairs (523 mothers, 528 neonates) were selected for the present study. The median age of the mothers was 25 years (IQR 23 to 29). 291 (55%) of 528 children were boys and 237 (45%) were girls, and most children (452 [86%]) were breastfed before the age of 6 months. The GMTs and the seroprevalence for the SWL4204/09 strain were higher than those for the SWL1277/16 and SWL185/18 strains among mothers (GMTs: 10·4 [95% CI 9·8 to 11·1] vs 9·3 [8·7 to 9·8] vs 8·0 [7·5 to 8·4], p<0·0001; seroprevalence: 11·1% [95% CI 8·5 to 14·1] vs 6·9% [4·9 to 9·4] vs 4·6% [3·0 to 6·8], p=0·0003) and among neonates (GMTs: 10·7 [10·0 to 11·5] vs 9·4 [8·8 to 10·0] vs 8·1 [7·6 to 8·6], p<0·0001; seroprevalence: 13·4% [10·7 to 16·7] vs 8·7% [6·5 to 11·5] vs 6·1% [4·2 to 8·5], p=0·0002). Regardless of the A(H1N1)pdm09-specific strain, maternal antibodies could be transferred efficiently via the placenta (mean transfer ratios: 1·10 for SWL4204/09 vs 1·09 for SWL1277/16 vs 1·06 for SWL185/18; p=0·93). The A(H1N1)pdm09 strain-specific antibodies waned below the protective threshold of 1:40 within 2 months after birth. After maternal antibody waning, there were periodic increases and decreases in HAI antibody titres against three A(H1N1)pdm09 strains, and such increases were all significantly associated with a higher immune response to heterologous strains. Vaccination against the SWL4204/09 strain was associated with a poor response to the SWL185/18 strain (β-0·20, 95% CI -0·28 to -0·13; p<0·0001).

INTERPRETATION

Our findings suggest low pre-existing immunity against influenza A(H1N1)pdm09 virus among unvaccinated Chinese adult female and paediatric populations. This evidence, together with the rapid decay of maternal antibodies and the observed cross-reactivity among different A(H1N1)pdm09 strains, highlights the importance of accelerating maternal and paediatric influenza vaccination in China.

FUNDING

The Key Program of the National Natural Science Foundation of China.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Outcomes and Risk Factor Analysis of Plastic Bronchitis Among 321 Children with Influenza Pneumonia After Bronchoscopy Examination

Background

Plastic bronchitis (PB) is a rare and severe lung disease. It can be triggered by influenza virus infection, which is a common respiratory infection in children. Bronchoscopy can aid in the early detection and treatment of PB. However, the outcomes and risk for PB development in pediatric patients with influenza virus infection are not fully understood.

Methods

Data from 321 children diagnosed with influenza virus pneumonia who underwent bronchoscopy examinations between 1st January, 2009 and 31st December, 2020 were retrospectively analyzed to assess the outcomes and risk factors associated with PB development.

Results

This study included 97 girls and 224 boys with influenza virus pneumonia with a median age of 42 months. Among them, 36 patients (11.2%) were categorized as having PB based on bronchoscopy findings. PB patients had significantly longer fever durations (p=0.010) and higher risks of developing severe conditions including respiratory failure (p<0.001), acute respiratory distress syndrome (p<0.001), and air-leak syndrome (p<0.001) compared to non-PB patients. Conventional treatment including the use of neuraminidase inhibitors and antibiotics did not differ between the PB and non-PB patients, but PB patients required more anti-inflammatory treatment (p=0.019) and ventilator support (p<0.001). Combined univariate and multivariate analyses suggested that radiographic findings, including mediastinal emphysema (p=0.012) and lung consolidation (p=0.012), as well as increased levels of neutrophils (p=0.026), aspartate aminotransferase (p=0.004), and lactate dehydrogenase (p<0.001), were identified as risk factors for PB development in patients with influenza virus pneumonia. Although PB patients required more intensive care and had longer hospital stays, they all recovered well after treatment.

Conclusion

Influenza virus infection is linked to PB development in children. Identifying risk factors and early intervention such as bronchoscopy can improve the prognosis of children with PB.

Safety and Immunogenicity of Enterovirus 71 Vaccine (Vero Cell) Administered Simultaneously with Trivalent Split-Virion Influenza Vaccine in Infants Aged 6-7 Months: A Phase 4, Randomized, Controlled Trial

Objective: To assess the immunogenicity and safety of the enterovirus 71 vaccine (Vero cell) (EV71 vaccine) and trivalent split-virion influenza vaccine (IIV3). Methods: Healthy infants aged 6-7 months were recruited from Zhejiang Province, Henan Province, and Guizhou Province and randomly assigned to the simultaneous vaccination group, EV71 group, and IIV3 group at a ratio of 1:1:1. Then, 3 mL blood samples were collected before vaccination and 28 days after the second dose of vaccine. Cytopathic effect inhibition assay was used to detect EV71 neutralization antibody, and cytopathic effect inhibition assay was used to detect influenza virus antibody. Results: A total of 378 infants were enrolled and received the first dose of vaccine and were included in the safety analysis, and 350 infants were involved in the immunogenicity analysis. The adverse events rates were 31.75%, 28.57%, and 34.13% in the simultaneous vaccination group, EV71 group, and IIV3 group (p > 0.05), respectively. No vaccine-related serious adverse events were reported. After two doses of EV71 vaccine, the seroconversion rates of EV71 neutralizing antibody were 98.26% and 97.37% in the simultaneous vaccination group and the EV71 group, respectively. After two doses of IIV3, the simultaneous vaccination group and the IIV3 group, respectively, had seroconversion rates of 80.00% and 86.78% for H1N1 antibody, 99.13% and 98.35% for H3N2 antibody, and 76.52% and 80.99% for B antibody. There was no statistically significant difference in the seroconversion rates of influenza virus antibodies between groups (p > 0.05). Conclusions: The coadministration of EV71 vaccine and IIV3 has good safety and immunogenicity in infants aged 6-7 months.

Cost-Effectiveness and Health Impacts of Different Influenza Vaccination Strategies for Children in China

INTRODUCTION

We aimed to evaluate the economic and health impacts of 3 influenza vaccines available in China, including trivalent inactivated vaccine, quadrivalent inactivated vaccine, and live attenuated influenza vaccine, for children aged 6 months to 18 years.

METHODS

Two decision-analytic models were developed to simulate 4 vaccination strategies. Outcomes included total costs from a societal perspective in 2021, quality-adjusted life-year loss, numbers of outpatient and inpatient cases, and deaths avoided using each strategy. Deterministic and probabilistic sensitivity analyses were performed to examine the uncertainty of model inputs.

RESULTS

For children aged 6 months to 3 years, trivalent inactivated vaccine saved $48 million and avoided a loss of 17,637 quality-adjusted life-years compared with no vaccination. For children aged 3-18 years, quadrivalent inactivated vaccine was cost-effective compared with trivalent inactivated vaccine, with an incremental cost-effectiveness ratio of $32,948.5/quality-adjusted life-year (willingness-to-pay threshold=$37,653/quality-adjusted life-year), which was sensitive to the RR of vaccine effectiveness of quadrivalent inactivated vaccine versus of trivalent inactivated vaccine. When compared with quadrivalent inactivated vaccine, live attenuated influenza vaccine was $1.28 billion more costly but gained an additional 13,560 quality-adjusted life-years; its incremental cost-effectiveness ratio was $123,983.8/quality-adjusted life-year. Live attenuated influenza vaccine would be cost-effective if its vaccine effectiveness was >0.79. Probabilistic sensitivity analysis revealed that quadrivalent inactivated vaccine, trivalent inactivated vaccine, live attenuated influenza vaccine, and no vaccination were cost-effective in 55.94%, 33.09%, 10.97%, and 0% of 10,000 Monte Carlo simulations.

CONCLUSIONS

Trivalent inactivated vaccine was cost-effective compared with no vaccination in children aged 6 months to 18 years. Of the 3 vaccination strategies for children aged 3-18 months, quadrivalent inactivated vaccine appears to be the most cost-effective.

Comparative effectiveness of oseltamivir versus peramivir for hospitalized children (aged 0-5 years) with influenza infection

OBJECTIVES

The effectiveness of oseltamivir versus peramivir in children infected with influenza remains unclear. This study aimed to evaluate their effectiveness in young children (aged 0-5 years) infected with severe influenza A virus (IAV) or influenza B virus (IBV).

METHODS

We analyzed a cohort of 1662 young children with either IAV (N = 1095) or IBV (N = 567) who received oseltamivir or peramivir treatment from January 1, 2018 to March 31, 2022. Propensity score matching methods were applied to match children who were oseltamivir-treated versus peramivir-treated.

RESULTS

Children who were IAV-infected and IBV-infected shared similar features, such as influenza-associated symptoms and comorbidities at baseline. Among children infected with IAV with bacterial coinfection, the recovery rate was significantly greater in children treated with oseltamivir than in children treated with peramivir (15.6% vs 4.4%, P = 0.01). The median duration of hospitalization was also shorter in children treated with oseltamivir. Among children infected with IAV without bacterial coinfection, the recovery rate was greater in children treated with oseltamivir than in children treated with peramivir (21.1% vs 3.7%, P = 0.002). However, oseltamivir and peramivir offered similar recovery rates and duration of hospitalization (P >0.05 for both) among children infected with IBV.

CONCLUSION

Oseltamivir and peramivir exhibit similar effectiveness in young children with severe influenza B, whereas oseltamivir demonstrated improved recovery and shorter hospitalization in the treatment of severe influenza A in hospitalized children.

Immunogenicity and safety of an inactivated enterovirus 71 vaccine coadministered with trivalent split-virion inactivated influenza vaccine: A phase 4, multicenter, randomized, controlled trial in China

Background

Few data exist on the immunogenicity and safety of an inactivated enterovirus 71 vaccine (EV71 vaccine) coadministered with trivalent split-virion inactivated influenza vaccine (IIV3) in infants.

Methods

This trial was a phase 4, randomized, controlled trial. Infants aged 6-11 months were eligible, with no history of hand, foot and mouth disease (HFMD) and no history of EV71 vaccine or any influenza vaccine. Eligible infants were randomly assigned to EV71+IIV3 group, EV71 group or IIV3 group. Blood samples were collected on day 0 and 56.

Results

Between September 2019 and June 2020, 1151 infants met eligibility criteria and 1134 infants were enrolled. 1045 infants were included in the per-protocol population, including 347 in the EV71+IIV3 group, 343 in the EV71 group, and 355 in the IIV3 group. The seroconversion rate (98.56% vs 98.54%; seroconversion rates difference of 0.02% [95% CI: 0.70-0.98]) and GMT (419.05 vs 503.72; GMT ratio of 0.83 [95% CI 0.70 - 0.98]) of EV71 neutralizing antibodies in the EV71+IIV3 group was not inferior to those in the EV71 group. The non-inferiority results for influenza virus antibodies (A/H1N1, A/H3N2 and B) showed that the seroconversion rates and GMTs of the EV71+IIV3 group were non-inferiority to those of the IIV3 group. Systemic and local adverse event rates were similar between groups. None of serious adverse events (SAEs) were related to vaccination.

Conclusions

Coadministration of the EV71 vaccine with IIV3 was safe and did not interfere with immunogenicity. These findings support a viable immunization strategy for infants with the EV71 vaccine coadministered with IIV3 in China. This trial is registered with ClinicalTrials.gov, number NCT04091880.

Parental preference for influenza vaccine for children in China: a discrete choice experiment

OBJECTIVES

To investigate what factors affect parents' influenza vaccination preference for their children and whether there exists preference heterogeneity among respondents in China.

DESIGN

Cross-sectional study. A discrete choice experiment was conducted. Five attributes were identified based on literature review and qualitative interviews, including protection rate, duration of vaccine-induced protection, risk of serious side effects, location of manufacturer and out-of-pocket cost.

SETTING

Multistage sampling design was used. According to geographical location and the level of economic development, 10 provinces in China were selected, and the survey was conducted at community healthcare centres or stations.

PARTICIPANTS

Parents with at least one child aged between 6 months and 5 years old were recruited and the survey was conducted via a face-to-face interview in 2019. In total, 600 parents completed the survey, and 449 who passed the internal consistency test were included in the main analysis.

MAIN OUTCOMES AND MEASURES

A mixed logit model was used to estimate factors affecting parents' preference to vaccinate their children. In addition, sociodemographic characteristics were included to explore the preference heterogeneity.

RESULTS

In general, respondents preferred to vaccinate their children. All attributes were statistically significant and among them, the risk of severe side effects was the most important attribute, followed by the protection rate and duration of vaccine-induced protection. Contrary to our initial expectation, respondents have a stronger preference for the domestic than the imported vaccine. Some preference heterogeneity among parents was also found and in particular, parents who were older, or highly educated placed a higher weight on a higher protection rate.

CONCLUSION

Vaccination safety and vaccine effectiveness are the two most important characteristics that influenced parents' decision to vaccinate against influenza for their children in China. Results from this study will facilitate future policy implementations to improve vaccination uptake rates.

Burden of severe illness associated with laboratory confirmed influenza in adults aged 50-64 years: A rapid review

BACKGROUND

While the high burden of illness caused by seasonal influenza in children and the elderly is well recognize, less is known about the burden in adults 50-64 years of age. The lack of data for this age group is a key challenge in evaluating the cost-effectiveness of immunization programs. We aimed to assess influenza-associated hospitalization and mortality rates and case fatality rates for hospitalized cases among adults aged 50-64 years.

METHODS

This rapid review was conducted according to the PRISMA; we searched MEDLINE, EMBASE, Cochrane, Web of Science, and grey literature for articles and reports published since 2010. Studies reporting rates of hospitalization and/or mortality associated with laboratory-confirmed influenza among adults 50-64 or 45-64 years of age for the 2010-11 through 2019-20 seasons were included.

RESULTS

Twenty studies from 13 countries were reviewed. Reported rates of hospitalization associated with laboratory-confirmed influenza were 5.7 to 112.8 per 100,000. Rates tended to be higher in the 2015-2019 compared with the 2010-2014 seasons and were higher in studies reporting data from high-income versus low and middle-income countries. Mortality rates were reported in only one study, with rates ranging from 0.8 to 3.5 per 100,000 in four different seasons. The case fatality rate among those hospitalized with influenza, as reported by population-based studies, ranged from 1.3% to 5.6%.

CONCLUSIONS

Seasonal influenza imposes a significant burden of morbidity on adults 50-64 years of age but with high heterogeneity across seasons and geographic regions. Ongoing surveillance is required to improve estimates of burden to better inform influenza vaccination and other public health policies.

Subtype H3N2 Influenza A Viruses: An Unmet Challenge in the Western Pacific

Subtype H3N2 influenza A viruses (A(H3N2)) have been the dominant strain in some countries in the Western Pacific region since the 2009 influenza A(H1N1) pandemic. Vaccination is the most effective way to prevent influenza; however, low vaccine effectiveness has been reported in some influenza seasons, especially for A(H3N2). Antigenic mismatch introduced by egg-adaptation during vaccine production between the vaccine and circulating viral stains is one of the reasons for low vaccine effectiveness. Here we review the extent of this phenomenon, the underlying molecular mechanisms and discuss recent strategies to ameliorate this, including new vaccine platforms that may provide better protection and should be considered to reduce the impact of A(H3N2) in the Western Pacific region.

Sentinel surveillance for influenza A viruses in Lahore District Pakistan in flu season 2015-2016

Background

Influenza A virus (IAV) remains an important global public health threat with limited epidemiological information available from low-and-middle-income countries. The major objective of this study was to describe the proportions, temporal and spatial distribution, and demographic and clinical characteristics of IAV positive patients with influenza like illness (ILI) and severe acute respiratory illness (SARI) in Lahore, Pakistan.

Methods

Prospective surveillance was established in a sentinel hospital from October 2015 to May 2016. All eligible outpatients and inpatients with ILI or SARI were enrolled in the study. Nasal and/or throat swabs were collected along with clinico-epidemiological data. Samples were tested by real-time RT-PCR (rRT-PCR) to identify IAV and subtype. The descriptive analysis of data was done in R software.

Results

Out of 311 enrolled patients, 284 (91.3%) were ILI and 27 (8.7%) were SARI cases. A distinct peak of ILI and SARI activity was observed in February. Fifty individuals (16%) were positive for IAV with peak positivity observed in December. Of 50 IAV, 15 were seasonal H3N2, 14 were H1N1pdm09 and 21 were unable to be typed. The majority of IAV positive cases (98%) presented with current or history of fever, 88% reported cough and 82% reported sore throat. The most common comorbidities in IAV positive cases were hepatitis C (4%), obesity (4%) and tuberculosis (6%). The highest incidence of patients reporting to the hospital was seen three days post symptoms onset (66/311) with 14 of these (14/66) positive for IAV.

Conclusion

Distinct trends of ILI, SARI and IAV positive cases were observed which can be used to inform public health interventions (vaccinations, hand and respiratory hygiene) at appropriate times among high-risk groups. We suggest sampling from both ILI and SARI patients in routine surveillance as recommended by WHO.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-07021-7.

Comparison of the incidence of bleeding between baloxavir marboxil and other anti-influenza drugs among outpatients with influenza virus infection: A retrospective cohort study using an employment-based health insurance claims database in Japan

Purpose

Alerts for bleeding events are included in the Japanese package inserts of some anti‐influenza drugs, including baloxavir marboxil and oseltamivir. However, there are few reports on the incidence of bleeding events during treatment with anti‐influenza drugs. This large‐scale quantitative assessment compared the incidence of bleeding events in influenza patients treated with baloxavir and other anti‐influenza drugs and in untreated patients.

Methods

This retrospective cohort study used a large‐scale Japanese employment‐based health insurance claims database provided by JMDC Inc. and included outpatients diagnosed with influenza between October 1, 2018 and April 11, 2019. Bleeding events were identified by International Classification of Diseases 10th revision codes. Incidences were compared between patients treated with baloxavir or neuraminidase inhibitors and untreated patients. Odds ratios were calculated after exact matching to adjust for potential confounders.

Results

Among 529 201 influenza episodes, 30 964 were untreated and 498 237 were treated with anti‐influenza drugs: baloxavir, 207 630; oseltamivir, 143 722; zanamivir, 28 208; peramivir, 5304; laninamivir, 113 373. Crude incidence proportions for total bleeding up to 20 days after influenza diagnosis were similar among treated groups, with a slightly higher value for peramivir (0.21% vs. 0.19% for baloxavir, oseltamivir, zanamivir, and laninamivir), and 0.30% in untreated patients. After exact matching, the incidence of bleeding for baloxavir was similar to that for other anti‐influenza treatments (odds ratios for baloxavir were 0.90–0.99 compared to other therapies).

Conclusions

Based on real‐world observation using a large‐scale claims database, a similar incidence of bleeding events was observed in recipients of the different anti‐influenza drugs.

Analysis of multimorbidity networks associated with different factors in Northeast China: a cross-sectional analysis

OBJECTIVES

This study aimed to identify and study the associations and co-occurrence of multimorbidity, and assessed the associations of diseases with sex, age and hospitalisation duration.

DESIGN

Cross-sectional.

SETTING

15 general hospitals in Jilin Province, China.

PARTICIPANTS

A total of 431 295 inpatients were enrolled through a cross-sectional study in Jilin Province, China.

PRIMARY OUTCOME MEASURES

The complex relationships of multimorbidity were presented as weighted networks.

RESULTS

The distributions of the numbers of diseases differed significantly by sex, age and hospitalisation duration (p<0.001). Cerebrovascular diseases (CD), hypertensive diseases (HyD), ischaemic heart diseases (IHD) and other forms of heart disease (OFHD) showed the highest weights in the multimorbidity networks. The connections between different sexes or hospitalisation duration and diseases were similar, while those between different age groups and diseases were different.

CONCLUSIONS

CD, HyD, IHD and OFHD were the central points of disease clusters and directly or indirectly related to other diseases or factors. Thus, effective interventions for these diseases should be adopted. Furthermore, different intervention strategies should be developed according to multimorbidity patterns in different age groups.

Burden of Influenza-Associated Respiratory Hospitalizations, Vietnam, 2014-2016

Influenza burden estimates are essential to informing prevention and control policies. To complement recent influenza vaccine production capacity in Vietnam, we used acute respiratory infection (ARI) hospitalization data, severe acute respiratory infection (SARI) surveillance data, and provincial population data from 4 provinces representing Vietnam’s major regions during 2014–2016 to calculate provincial and national influenza-associated ARI and SARI hospitalization rates. We determined the proportion of ARI admissions meeting the World Health Organization SARI case definition through medical record review. The mean influenza-associated hospitalization rates per 100,000 population were 218 (95% uncertainty interval [UI] 197–238) for ARI and 134 (95% UI 119–149) for SARI. Influenza-associated SARI hospitalization rates per 100,000 population were highest among children <5 years of age (1,123; 95% UI 946–1,301) and adults >65 years of age (207; 95% UI 186–227), underscoring the need for prevention and control measures, such as vaccination, in these at-risk populations.

Influenza epidemiology and burden of disease in Mongolia, 2013-2014 to 2017-2018

Background

Mongolia is a vast, sparsely populated country in central Asia. Its harsh climate and nomadic lifestyle make the population vulnerable to acute respiratory infections, particularly influenza. Evidence on the morbidity, mortality and socioeconomic impact of influenza in Mongolia is scarce; however, routine surveillance for influenza-like illness (ILI), severe acute respiratory infection (SARI) and laboratory-detected influenza is conducted. This paper describes the epidemiology of influenza and the estimated burden of influenza-associated illness in Mongolia in the five influenza seasons between 2013–2014 and 2017–2018.

Methods

Demographic and laboratory data from 152 sentinel surveillance sites on all patients who met the case definitions of ILI and SARI between October 2013 and May 2018 were extracted and analysed as described in A Manual for Estimating Disease Burden Associated with Seasonal Influenza.

Results

The estimated annual influenza-associated ILI and SARI rates, presented as ranges, were 1279–2798 and 81–666 cases per 100 000 population, respectively. Children aged < 5 years accounted for 67% of all ILI cases and 79% of all SARI cases. The annual specimen positivity for influenza was highest (11–30% for ILI and 8–31% for SARI) for children aged 5– < 15 years and children < 2 years old, respectively. The annual mortality rate due to pneumonia and SARI was highest among children aged < 2 years (15.8–54.0 per 100 000 population). Although the incidence of influenza-associated ILI and SARI was lowest for people aged ³65 years, the mortality rate due to pneumonia and SARI (1.2–5.1 per 100 000) was higher than that for those aged 15–64 years.

Conclusion

The estimated influenza-associated ILI and SARI incidence rates are high in Mongolia, and children, especially those aged < 5 years, have the highest influenza-associated burden in Mongolia. These findings provide evidence for decision-makers in Mongolia to consider targeted influenza vaccination, particularly for children.

Development of influenza-associated disease burden pyramid in Shanghai, China, 2010-2017: a Bayesian modelling study

OBJECTIVES

Negative estimates can be produced when statistical modelling techniques are applied to estimate morbidity and mortality attributable to influenza. Based on the prior knowledge that influenza viruses are hazardous pathogens and have adverse health outcomes of respiratory and circulatory disease (R&C), we developed an improved model incorporating Bayes' theorem to estimate the disease burden of influenza in Shanghai, China, from 2010 to 2017.

DESIGN

A modelling study using aggregated data from administrative systems on weekly R&C mortality and hospitalisation, influenza surveillance and meteorological data. We constrained the regression coefficients for influenza activity to be positive by truncating the prior distributions at zero.

SETTING

Shanghai, China.

PARTICIPANTS

People registered with R&C deaths (450 298) and hospitalisations (2621 787, from 1 July 2013), and with influenza-like illness (ILI) outpatient visits (342 149) between 4 January 2010 and 31 December 2017.

PRIMARY OUTCOME MEASURES

Influenza-associated disease burden (mortality, hospitalisation and outpatient visit rates) and clinical severity (outpatient-mortality, outpatient-hospitalisation and hospitalisation-mortality risks).

RESULTS

Influenza was associated with an annual average of 15.49 (95% credibility interval (CrI) 9.06-22.06) excess R&C deaths, 100.65 (95% CrI 48.79-156.78) excess R&C hospitalisations and 914.95 (95% CrI 798.51-1023.66) excess ILI outpatient visits per 100 000 population in Shanghai. 97.23% and 80.24% excess R&C deaths and hospitalisations occurred in people aged ≥65 years. More than half of excess morbidity and mortality were associated with influenza A(H3N2) virus, and its severities were 1.65-fold to 3.54-fold and 1.47-fold to 2.16-fold higher than that for influenza A(H1N1) and B viruses, respectively.

CONCLUSIONS

The proposed Bayesian approach with reasonable prior information improved estimates of influenza-associated disease burden. Influenza A(H3N2) virus was generally associated with higher morbidity and mortality, and was relatively more severe compared with influenza A(H1N1) and B viruses. Targeted influenza prevention and control strategies for the elderly in Shanghai may substantially reduce the disease burden.

Preference of influenza vaccination among the elderly population in Shaanxi province, China

The influenza vaccination uptake rate is low in China. In the current study, we aimed to explore the preferences of influenza vaccination among the Chinese elderly. A discrete choice experiment design was performed to assess their preferences toward five influenza vaccination attributes, including vaccine effectiveness, duration of protection, severe adverse effects, vaccination cost, and vaccination recommendation source. A total of 144 participants aged over 60 years from three cities of Shaanxi province in China were surveyed. A mixed logit model was employed to analyze the data. The elderly population were found to prefer influenza vaccination with a longer duration of protection, followed by lower severe adverse effects, higher vaccine effectiveness, and recommended by healthcare providers. The vaccination cost was the least important attribute. The most considerable marginal willingness to pay for vaccination (CNY220.90) and the highest vaccination choice probability (83.70%) occurred when the duration of protection extended from 3 to 12 months. The present study's findings would inform decision-makers on implementing appropriate interventions for the increase of influenza vaccination coverage among the elderly in China.

Etiological and epidemiological characteristics of severe acute respiratory infection caused by multiple viruses and Mycoplasma pneumoniae in adult patients in Jinshan, Shanghai: A pilot hospital-based surveillance study

Background

Severe acute respiratory infection (SARI) results in a tremendous disease burden worldwide. Available research on active surveillance among hospitalized adult patients suffering from SARI in China is limited. This pilot study aimed to identify associated etiologies and describe the demographic, epidemiological and clinical profiles of hospitalized SARI patients aged over 16 years in Jinshan, Shanghai.

Methods

Active surveillance was conducted at 1 sentinel hospital in Jinshan district, Shanghai, from April 2017 to March 2018. Hospitalized SARI patients aged over 16 years old were enrolled, and nasopharyngeal swabs were collected within 24 hours of admission and tested for multiple respiratory viruses (including 18 common viruses) and Mycoplasma pneumoniae with real-time polymerase chain reaction. Demographic, epidemiological and clinical information was obtained from case report forms.

Results

In total, 397 SARI patients were enrolled; the median age was 68 years, and 194 (48.9%) patients were male. A total of 278 (70.0%) patients had at least one underlying chronic medical condition. The most frequent symptoms were cough (99.2%) and sputum production (88.4%). The median duration of hospitalization was 10 days. A total of 250 infection patients (63.0%) were positive for at least one pathogen, of whom 198 (49.9%) were positive for a single pathogen and 52 (13.1%) were positive for multiple pathogens. The pathogens identified most frequently were M. pneumoniae (23.9%, 95/397), followed by adenovirus (AdV) (11.6%, 46/397), influenza virus A/H3N2 (Flu A/H3N2) (11.1%, 44/397), human rhinovirus (HRhV) (8.1%, 32/397), influenza virus B/Yamagata (Flu B/Yamagata) (6.3%, 25/397), pandemic influenza virus A/H1N1 (Flu A/pH1N1) (4.0%, 16/397), parainfluenza virus (PIV) type 1 (2.0%, 8/397), human coronavirus (HCoV) type NL63 (2.0%, 8/397), HCoV 229E (1.5%, 6/397), HCoV HKU1 (1.5%, 6/397), PIV 3 (1.5%, 6/397), human metapneumovirus (HMPV) (1.5%, 6/397), PIV 4 (1.3%, 5/397), HCoV OC43 (1.0%, 4/397), influenza virus B/Victoria (Flu B/Victoria) (0.5%, 2/397), respiratory syncytial virus (RSV) type B (0.5%, 2/397), and human bocavirus (HBoV) (0.3%, 1/397). The seasonality of pathogen-confirmed SARI patients had a bimodal distribution, with the first peak in the summer and the second peak in the winter. Statistically significant differences were observed with respect to the rates of dyspnea, radiographically diagnosed pneumonia and the presence of at least one comorbidity in patients who were infected with only M. pneumoniae, AdV, HRhV, Flu A/H3N2, Flu A /pH1N1 or Flu B/Yamagata. The differences in the positivity rates of the above 6 pathogens among the different age groups were nonsignificant.

Conclusions

M. pneumoniae, AdV and Flu A/H3N2 were the main pathogens detected in hospitalized SARI patients aged over 16 years old in Jinshan district, Shanghai. Our findings highlight the importance of sustained multipathogen surveillance among SARI patients in sentinel hospitals, which can provide useful information on SARI etiologies, epidemiology, and clinical characteristics.

Influenza-associated disease burden in mainland China: a systematic review and meta-analysis

Influenza causes substantial morbidity and mortality. Many original studies have been carried out to estimate disease burden of influenza in mainland China, while the full disease burden has not yet been systematically reviewed. We did a systematic review and meta-analysis to assess the burden of influenza-associated mortality, hospitalization, and outpatient visit in mainland China. We searched 3 English and 4 Chinese databases with studies published from 2005 to 2019. Studies reporting population-based rates of mortality, hospitalization, or outpatient visit attributed to seasonal influenza were included in the analysis. Fixed-effects or random-effects model was used to calculate pooled estimates of influenza-associated mortality depending on the degree of heterogeneity. Meta-regression was applied to explore the sources of heterogeneity. Publication bias was assessed by funnel plots and Egger’s test. We identified 30 studies eligible for inclusion with 17, 8, 5 studies reporting mortality, hospitalization, and outpatient visit associated with influenza, respectively. The pooled influenza-associated all-cause mortality rates were 14.33 and 122.79 per 100,000 persons for all ages and ≥ 65 years age groups, respectively. Studies were highly heterogeneous in aspects of age group, cause of death, statistical model, geographic location, and study period, and these factors could explain 60.14% of the heterogeneity in influenza-associated mortality. No significant publication bias existed in estimates of influenza-associated all-cause mortality. Children aged < 5 years were observed with the highest rates of influenza-associated hospitalizations and ILI outpatient visits. People aged ≥ 65 years and < 5 years contribute mostly to mortality and morbidity burden due to influenza, which calls for targeted vaccination policy for older adults and younger children in mainland China.

Economic burden of influenza illness among children under 5 years in Suzhou, China: Report from the cost surveys during 2011/12 to 2016/17 influenza seasons

BACKGROUND

Data are limited on the economic burden of seasonal influenza in China. We estimated the cost due to influenza illness among children < 5-year-old in Suzhou, China.

METHODS

This study adopted a societal perspective to estimate direct medical cost, direct non-medical cost, and indirect cost related to lost productivity. Data to calculate costs and rates of three influenza illness outcomes (non-medically attended, outpatient and hospitalization) were collected from prospective community-based cohort studies and hospital-based enhanced laboratory-confirmed influenza surveillance in Suzhou during the 2011/12 to 2016/17 influenza seasons. We used mean cost-per-episode, annual incidence rates of episodes of each outcome, and annual population size to estimate the total annual economic burden of influenza illnesses among children < 5-year-old for Suzhou. All costs were reported in 2017 U.S. dollars.

RESULTS

The mean cost-per-episode (standard deviation) was $9.92 (13.26) for non-medically attended influenza, $161.05 (176.98) for influenza outpatient illnesses, and $1425.95 (603.59) for influenza hospitalizations. By applying the annual incidence rates to the population size, we estimated an annual total of 4,919 episodes of non-medically attended influenza, 21,994 influenza outpatient, and 2,633 influenza hospitalization. Total annual economic burden of influenza to society among children < 5-year-old in Suzhou was $7.37 (95% confidence interval, 6.9-7.8) million, with estimated costs for non-medically attended influenza of $49,000 (46,000-52,000), influenza outpatients $3.5 (3.3-3.8) million, and influenza hospitalizations $3.8 (3.6-3.9) million. Among outpatients, the indirect cost was 36.3% ($1.3 million) of total economic burden, accounting for 21,994 days of lost productivity annually. Among inpatients, the indirect cost was 22.1% ($829,000), accounting for 18,431 days of lost productivity annually.

CONCLUSIONS

Our findings show that influenza in children < 5-year-oldcauses substantial societal economic burden in Suzhou, China. Assessing the potential economic benefit of increasing influenza vaccination coverage in this population is warranted.

Estimated influenza illnesses and hospitalizations averted by influenza vaccination among children aged 6-59 months in Suzhou, China, 2011/12 to 2015/16 influenza seasons

BACKGROUND

There are few estimates of vaccination-averted influenza-associated illnesses in China.

METHODS

We used a mathematical model and Monte Carlo algorithm to estimate numbers and 95% confidence intervals (CI) of influenza-associated outcomes (hospitalization, illness, and medically-attended (MA) illness) averted by vaccination among children aged 6-59 months in Suzhou from October 2011-September 2016. Influenza illnesses included non-hospitalized MA influenza illnesses and non-MA influenza illnesses. The numbers of influenza-associated outcomes averted by vaccination were the difference between the expected burden if there were no vaccination given and the observed burden with vaccination. The model incorporated the disease burden estimated based on surveillance data from Suzhou University Affiliated Children's Hospital (SCH) and data from health utilization surveys conducted in the catchment area of SCH, age-specific estimates of influenza vaccination coverage in Suzhou from the Expanded Program on Immunization database, and influenza vaccine effectiveness estimates from previous publications. Averted influenza estimations were presented as absolute numbers and in terms of the prevented fraction (PF). A hypothetical scenario with 50% coverage (but identical vaccine effectiveness) over the study period was also modeled.

RESULTS

In ~250,000 children, influenza vaccination prevented an estimated 731 (CI: 549-960) influenza hospitalizations (PF: 6.2% of expected, CI: 5.8-6.6%) and 10,024 (7593-12,937) influenza illnesses (PF: 6.5%, 6.4-6.7%), of which 8342 (6338-10,768) were MA (PF: 6.6%, 6.4-6.7%) from 2011 to 2016. The PFs declined each year along with decreasing influenza vaccination coverage. If 50% of the study population had been vaccinated over time, the estimated numbers of averted cases during the study period would have been 4059 (3120-5762) influenza hospitalizations (PF: 27.2%, 26.4-27.9%) and 56,215 (42,925-78,849) influenza illnesses (PF: 28.5%, 28.3-28.7%), of which 46,596 (35,662-65,234) would be MA (PF: 28.5%, 28.3-28.7%).

CONCLUSION

Influenza vaccination is estimated to have averted influenza-associated illness outcomes even with low coverage in children aged 6-59 months in Suzhou. Increasing influenza vaccination coverage in this population could further reduce illnesses and hospitalizations.

Epidemiology of Influenza among patients with influenza-like illness and severe acute respiratory illness in Pakistan: A 10-year surveillance study 2008-17

In Pakistan, the burden of influenza was largely unknown, as no formal surveillance system was in place. In 2008, an influenza surveillance system was set up in eight sentinel sites. This study describes the epidemiology of influenza virus using a 10-year surveillance data from 2008 to 2017. Nasopharyngeal/throat swabs were collected from patients with influenza-like illness (ILI) and severe acute respiratory illness (SARI) along with relevant epidemiological information. The samples were tested using real-time reverse transcriptase-polymerase chain reaction for the detection and characterization of influenza viruses. A total of 17 209 samples were tested for influenza, out of which 3552 (20.6%) were positive; 2151/11 239 (19.1%) were patients with ILI, whereas 1401/5970 (23.5%) were patients with SARI. Influenza A/H1N1pdm09 was the predominant strain with 40.6% (n = 1442) followed by influenza B (936, 26.4%). Influenza A/H1N1pdm09 was predominant among the children (5-14 years) and adults (15-64 years). Influenza B strain was predominantly found in the elderly age group (≥ 65 years) accounting for 48% of cases followed by children (2-4 years) accounting for 37% of cases. This 10-year surveillance data provides evidence of influenza activity in the country throughout the year with seasonal winter peaks. The results could be used to strengthen the epidemic preparedness and response plan.

Epidemiology of influenza in hospitalized children with respiratory tract infection in Suzhou area from 2016 to 2019

Influenza is a contagious respiratory disease and risks public health in China, and it has caused wide public concern in recent years. Immunocompromised patients, such as children and elderly people, suffer more severe influenza complication and some extreme cases are even life threatening. To identify the influenza characteristics and its correlation with various climatic and environmental pollution factors, we collected the reported influenza epidemic of hospitalized children in Children's Hospital of Soochow University from 2016 to 2019. Our results show that the main influenza virus subtypes are A/H1N1, A/H3N2, B/BV, and B/BY. We also identified the characteristics of the prevalent influenza virus subtypes in different months, seasons, years, and patients' age. Of all the influenza infected patients, the most susceptible groups are children over 3 to 5 years of age, and more cases are reported in winter than other seasons. We also found that influenza is also highly correlated with climatic and environmental pollution factors, and the autoregressive integrated moving average model is employed for the short-term influenza prediction in Suzhou city, which can provide scientific basis for the prevention and control of influenza and public health decision-making.

Disease burden and clinical severity of the first pandemic wave of COVID-19 in Wuhan, China

The novel coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, where the initial wave of intense community transmissions was cut short by interventions. Using multiple data sources, here we estimate the disease burden and clinical severity by age of COVID-19 in Wuhan from December 1, 2019 to March 31, 2020. Our estimates account for the sensitivity of the laboratory assays, prospective community screenings, and healthcare seeking behaviors. Rates of symptomatic cases, medical consultations, hospitalizations and deaths were estimated at 796 (95% CI: 703-977), 489 (472-509), 370 (358-384), and 36.2 (35.0-37.3) per 100,000 persons, respectively. The COVID-19 outbreak in Wuhan had a higher burden than the 2009 influenza pandemic or seasonal influenza in terms of hospitalization and mortality rates, and clinical severity was similar to that of the 1918 influenza pandemic. Our comparison puts the COVID-19 pandemic into context and could be helpful to guide intervention strategies and preparedness for the potential resurgence of COVID-19.

Disease burden and clinical severity of the first pandemic wave of COVID-19 in Wuhan, China

The pandemic of novel coronavirus disease 2019 (COVID-19) began in Wuhan, China, where a first wave of intense community transmission was cut short by interventions. Using multiple data source, we estimated the disease burden and clinical severity of COVID-19 by age in Wuhan from December 1, 2019 to March 31, 2020. We adjusted estimates for sensitivity of laboratory assays and accounted for prospective community screenings and healthcare seeking behaviors. Rates of symptomatic cases, medical consultations, hospitalizations and deaths were estimated at 796 (95%CI: 703-977), 489 (472-509), 370 (358-384), and 36.2 (35.0-37.3) per 100,000 persons, respectively. The COVID-19 outbreak in Wuhan had higher burden than the 2009 influenza pandemic or seasonal influenza, and that clinical severity was similar to that of the 1918 influenza pandemic. Our comparison puts the COVID-19 pandemic into context and could be helpful to guide intervention strategies and preparedness for the potential resurgence of COVID-19.

Virus detections among patients with severe acute respiratory illness, Northern Vietnam

Severe acute respiratory illness (SARI) is a major cause of death and morbidity in low- and middle-income countries, however, the etiologic agents are often undetermined due to the lack of molecular diagnostics in hospitals and clinics. To examine evidence for select viral infections among patients with SARI in northern Vietnam, we studied 348 nasopharyngeal samples from military and civilian patients admitted to 4 hospitals in the greater Hanoi area from 2017–2019. Initial screening for human respiratory viral pathogens was performed in Hanoi, Vietnam at the National Institute of Hygiene and Epidemiology (NIHE) or the Military Institute of Preventative Medicine (MIPM), and an aliquot was shipped to Duke-NUS Medical School in Singapore for validation. Patient demographics were recorded and used to epidemiologically describe the infections. Among military and civilian cases of SARI, 184 (52.9%) tested positive for one or more respiratory viruses. Influenza A virus was the most prevalent virus detected (64.7%), followed by influenza B virus (29.3%), enterovirus (3.8%), adenovirus (1.1%), and coronavirus (1.1%). Risk factor analyses demonstrated an increased risk of influenza A virus detection among military hospital patients (adjusted OR, 2.0; 95% CI, 1.2–3.2), and an increased risk of influenza B virus detection among patients enrolled in year 2017 (adjusted OR, 7.9; 95% CI, 2.7–22.9). As influenza A and B viruses were commonly associated with SARI and are treatable, SARI patients entering these hospitals would benefit if the hospitals were able to adapt onsite molecular diagnostics.

Immunogenicity and safety of an inactivated quadrivalent influenza vaccine: a randomized, double-blind, controlled phase III clinical trial in children aged 6-35 months in China

Mismatch between circulating influenza B viruses and vaccine strains occurs frequently. In a randomized, double-blind, controlled phase III clinical study, healthy children aged 6-35 months were randomized into three groups at a ratio of 2:1:1, received two doses of quadrivalent influenza vaccines (QIVs) or licensed trivalent influenza vaccines (TIVs). The primary objective was to evaluate the non-inferiority immunogenicity of QIV compared with the two TIVs, containing B/Victoria or B/Yamagata strain. Safety information was collected for 28 days after each vaccination. Serious adverse events (SAEs) were monitored for 6 months after the second vaccination. A total of 2146 subjects (QIV: 1069, TIV-Vic: 540, TIV-Yam: 537) were enrolled in this study. QIV was found non-inferior to TIVs for shared strains (A/H1N1 and A/H3N2) and corresponding BY strain based on hemagglutination inhibition (HI) antibodies 28 days after the second dose of vaccination. The resulted geometric mean titer (GMT) ratios (QIV/TIV) were 0.98 (0.89, 1.07) for H1N1, 0.95 (0.85, 1.05) for H3N2 and 0.89 (0.81, 0.98) for BY. And the seroconversion rate differences (QIV-TIV) were -0.46% (-3.24%, 2.31%) for H1N1, -1.95% (-5.54%, 1.65%) for H3N2 and -3.58% (-8.11%, 0.95%) for BY. The BV strain in QIV did not reach the non-inferiority criteria, with GMT of 1:52.25 (vs. 1:61.02 of TIV-Vic) and seroconversion rate of 59.49% (vs. 66.85% of TIV-Vic). No increased safety concerns occurred in QIV group. Candidate QIV can provide good protection for children aged 6 to 35 months, and its immunogenicity and safety were proved.

CLINICAL TRIALS REGISTRATION

ClinicalTrials.gov number: NCT03859141.

Cost-effectiveness of introducing national seasonal influenza vaccination for adults aged 60 years and above in mainland China: a modelling analysis

BACKGROUND

China has an aging population with an increasing number of adults aged ≥ 60 years. Influenza causes a heavy disease burden in older adults, but can be alleviated by vaccination. We assessed the cost-effectiveness of a potential government-funded seasonal influenza vaccination program in older adults in China.

METHODS

We characterized the health and economic impact of a fully funded influenza vaccination program for older adults using China-specific influenza disease burden, and related cost data, etc. Using a decision tree model, we calculated the incremental costs per quality-adjusted life year (QALY) gained of vaccination from the societal perspective, at a willingness-to-pay threshold equivalent to GDP per capita (US$8840). Moreover, we estimated the threshold vaccination costs, under which the fully funded vaccination program is cost-effective using GDP per capita as the willingness-to-pay threshold.

RESULTS

Compared to current self-paid vaccination, a fully funded vaccination program is expected to prevent 19,812 (95% uncertainty interval, 7150-35,783) influenza-like-illness outpatient consultations per year, 9418 (3386-17,068) severe acute respiratory infection hospitalizations per year, and 8800 (5300-11,667) respiratory excess deaths due to influenza per year, and gain 70,212 (42,106-93,635) QALYs per year. Nationally, the incremental costs per QALY gained of the vaccination program is US$4832 (3460-8307), with a 98% probability of being cost-effective. The threshold vaccination cost is US$10.19 (6.08-13.65). However, variations exist between geographical regions, with Northeast and Central China having lower probabilities of cost-effectiveness.

CONCLUSIONS

Our results support the implementation of a government fully funded older adult vaccination program in China. The regional analysis provides results across settings that may be relevant to other countries with similar disease burden and economic status, especially for low- and middle-income countries where such analysis is limited.

Recommendations for influenza and Streptococcus pneumoniae vaccination in elderly people in China

Influenza and pneumonia can be prevented by vaccination, but they remain major causes of morbidity and mortality in age-related diseases. In most areas of China, the rates of influenza and pneumococcal vaccination are relatively low and public awareness of vaccination remains insufficient. Thus, it is essential to recommend influenza and Streptococcus pneumoniae vaccination to elderly people in clinical practice. Based on recently published studies and related documents issued by several vaccination authorities, such as the World Health Organization, the National Health and Wellness Committee, the Chinese Center for Disease Control and Prevention, the US Centers for Disease Control and Prevention, and the US Advisory Committee on Immunization Practices, we propose official recommendations for influenza and S pneumoniae vaccination in elderly people in China.

A model of influenza infection and vaccination in children aged under 5 years in Beijing, China

BACKGROUND

Children aged under 5 years are particularly vulnerable to influenza infection. In this study, we aim to estimate the number and incidence of influenza among young children and estimate the impact of childhood vaccination in different scenarios from 2013/14 to 2016/17 seasons.

METHODS

The number and incidence rate of influenza infections among children aged under 5 years in Beijing was estimated by scaling up observed surveillance data. Then, we used a susceptible-exposed-infected-recovery (SEIR) model to reproduce the weekly number of influenza infections estimated in Beijing during the study seasons, and to estimate the number and proportion of influenza-attributed medically attended acute respiratory infections (I-MAARI) averted by vaccination in each season. Finally, we evaluated the impact of alternative childhood vaccination programs with different coverage and speed of vaccine distribution.

RESULTS

The estimated average annual incidence of influenza in children aged under 5 years was 33.9% (95% confidence interval (CI): 27.5%, 47.2%) during the study period. With the actual coverage during the included seasons at around 2.9%, an average of 3.9% (95%CI: 3.5%, 4.4%) I-MAARI was reduced compared to a no-vaccination scenario. Reaching 20%, 40%, 50%, 60%, 80% and 100% vaccine coverage would lead to an overall I-MAARI reduction of 25.3%, 42.7%, 51.9%, 57.0%, 65.3% and 71.2%. At 20% coverage scenario, an average of 28.8% I-MAARI will be prevented if intensive vaccination implemented in 2 months since the vaccine released.

CONCLUSION

In Beijing, the introduction of a program for vaccinating young children, even at relatively low vaccine coverage rates, would considerably reduce I-MAARI, particularly if the vaccines can be quickly delivered.

Spatiotemporal Analysis of Influenza in China, 2005-2018

Influenza is a major cause of morbidity and mortality worldwide, as well as in China. Knowledge of the spatial and temporal characteristics of influenza is important in evaluating and developing disease control programs. This study aims to describe an accurate spatiotemporal pattern of influenza at the prefecture level and explore the risk factors associated with influenza incidence risk in mainland China from 2005 to 2018. The incidence data of influenza were obtained from the Chinese Notifiable Infectious Disease Reporting System (CNIDRS). The Besag York Mollié (BYM) model was extended to include temporal and space-time interaction terms. The parameters for this extended Bayesian spatiotemporal model were estimated through integrated nested Laplace approximations (INLA) using the package R-INLA in R. A total of 702,226 influenza cases were reported in mainland China in CNIDRS from 2005–2018. The yearly reported incidence rate of influenza increased 15.6 times over the study period, from 3.51 in 2005 to 55.09 in 2008 per 100,000 populations. The temporal term in the spatiotemporal model showed that much of the increase occurred during the last 3 years of the study period. The risk factor analysis showed that the decreased number of influenza vaccines for sale, the new update of the influenza surveillance protocol, the increase in the rate of influenza A (H1N1)pdm09 among all processed specimens from influenza-like illness (ILI) patients, and the increase in the latitude and longitude of geographic location were associated with an increase in the influenza incidence risk. After the adjusting for fixed covariate effects and time random effects, the map of the spatial structured term shows that high-risk areas clustered in the central part of China and the lowest-risk areas in the east and west. Large space-time variations in influenza have been found since 2009. In conclusion, an increasing trend of influenza was observed from 2005 to 2018. The insufficient flu vaccine supplements, the newly emerging influenza A (H1N1)pdm09 and expansion of influenza surveillance efforts might be the major causes of the dramatic changes in outbreak and spatio-temporal epidemic patterns. Clusters of prefectures with high relative risks of influenza were identified in the central part of China. Future research with more risk factors at both national and local levels is necessary to explain the changing spatiotemporal patterns of influenza in China.

Cost-effectiveness of quadrivalent versus trivalent influenza vaccine for elderly population in China

BACKGROUND

Influenza-associated excess death occurred most in the elderly. We aimed to assess the cost-effectiveness of quadrivalent influenza vaccine (QIV) versus trivalent influenza vaccine (TIV) for prevention of influenza infection among elderly population in China.

METHODS

A decision-analytic model was developed to compare 1-year clinical and economic outcomes of three influenza vaccination options (no vaccination, TIV, and QIV) in a hypothetical cohort of Chinese elderly aged 69 years. Outcome measures included cost, influenza infection rate, influenza-related mortality rate, quality-adjusted life-years (QALY) loss, and incremental cost-effectiveness ratio (ICER) from societal perspective. Sensitivity analyses were performed to examine the uncertainty of model inputs.

RESULTS

Base-case results showed no vaccination was dominated (more costly at higher QALY loss) by TIV and QIV. QIV was more costly (USD56.29 versus USD54.28) with lower influenza infection rate (0.608 versus 0.623), mortality rate (0.00199 versus 0.00204), and QALY loss (0.01213 versus 0.01243) than TIV. QIV was cost-effective compared to TIV with ICER of 6,700 USD/QALY below the willingness-to-pay threshold (29,580 USD/QALY). One-way sensitivity analysis found the cost-effectiveness of QIV was subject to the relative risk of vaccine effectiveness of QIV versus TIV, and TIV would be cost-effective if the relative risk was below 1.05. In 10,000 Monte Carlo simulations, the probabilities of QIV, TIV, and no vaccination to be cost-effective were 86.3%, 13.7%, and 0%, respectively.

CONCLUSION

QIV appears to be a cost-effective option compared to TIV and no influenza vaccination for elderly population in China.

Hospitalizations for Influenza-Associated Severe Acute Respiratory Infection, Beijing, China, 2014-2016

We analyzed surveillance data for 2 sentinel hospitals to estimate the influenza-associated severe acute respiratory infection hospitalization rate in Beijing, China. The rate was 39 and 37 per 100,000 persons during the 2014–15 and 2015–16 influenza seasons, respectively. Rates were highest for children <5 years of age.

Influenza-associated Hospitalization in Children Younger Than 5 Years of Age in Suzhou, China, 2011-2016

BACKGROUND

Studying the burden and risk factors associated with severe illness from influenza infection in young children in eastern China will contribute to future cost-effectiveness analyses of local influenza vaccine programs.

METHODS

We conducted prospective, severe acute respiratory infection (SARI) surveillance at Suzhou University-Affiliated Children's Hospital to estimate influenza-associated hospitalizations in Suzhou University-Affiliated Children's Hospital by month in children younger than 5 years of age from October 2011 to September 2016. SARI was defined as fever (measured axillary temperature ≥ 38°C) and cough or sore throat or inflamed/red pharynx in the 7 days preceding hospitalization. We combined SARI surveillance data with healthcare utilization survey data to estimate and characterize the burden of influenza-associated SARI hospitalizations in Suzhou within this age group in the 5-year period.

RESULTS

Of the 36,313 SARI cases identified, 2,297 from respiratory wards were systematically sampled; of these, 259 (11%) were influenza positive. Estimated annual influenza-associated SARI hospitalization rates per 1,000 children younger than 5 years of age ranged from 4 (95% confidence interval [CI], 2-5) in the 2012-2013 season to 16 (95% CI, 14-19) in the 2011-2012 season. The predominant viruses were A/H3N2 (59%) in 2011-12, both A/H1N1pdm09 (42%) and B (46%) in 2012-13, A/H3N2 (71%) in 2013-14, A/H3N2 (55%) in 2014-15 and both A/H1N1pdm09 (50%) and B (50%) in 2015-16. The age-specific influenza-associated SARI hospitalization rates for the 5-year period were 11 (95% CI, 8-15) per 1,000 children 0-5 months of age; 8 (95% CI, 7-10) per 1,000 children 6-23 months of age and 5 (95% CI, 4-5) per 1,000 children 24-59 months of age, respectively.

CONCLUSIONS

From 2011 to 2016, influenza-associated SARI hospitalization rates in children aged younger than 5 years of age in Suzhou, China, were high, particularly among children 0-5 months of age. Higher hospitalization rates were observed in years where the predominant circulating virus was influenza A/H3N2. Immunization for children > 6 months, and maternal and caregiver immunization for those < 6 months, could reduce influenza-associated hospitalizations in young children in Suzhou.

Immunogenicity and safety of a trivalent inactivated influenza vaccine produced in Shenzhen, China versus a comparator influenza vaccine: a phase IV randomized study

Seasonal influenza causes substantial morbidity and mortality in China, which largely results from limited vaccine accessibility and poor vaccination coverage. Since 2013, Sanofi Pasteur's facilities in Shenzhen, China have produced a trivalent inactivated influenza vaccine (Shz-IIV3) for each influenza season according to Chinese pharmacopeia requirements. However, the immunogenicity of Shz-IIV3 has not been compared to existing Chinese trivalent inactivated influenza vaccines (IIV3s). Here, we describe the results of a phase IV, observer-blind, randomized study to evaluate whether the immunogenicity of Shz-IIV3 was non-inferior to a comparator IIV3 (Hualan Biological Engineering Inc) also manufactured and licensed in China. Healthy adults aged 18-59 years were randomly assigned in a 1:1 ratio to receive a single 0.5-mL intramuscular injection of the 2017-2018 Northern Hemisphere formulation of Shz-IIV3 (n = 800) or the comparator IIV3 (n = 799). Between baseline and day 28 after vaccination, hemagglutination inhibition titers for the three vaccine strains increased by at least 4-fold and were of similar magnitude in Shz-IIV3 and comparator IIV3 recipients. The rate of seroconversion or significant increase in titers was 62% to 92% in Shz-IIV3 recipients, and 63% to 91% in comparator IIV3 recipients. Post-vaccination hemagglutination inhibition titers and seroconversion rates for Shz-IIV3 were statistically non-inferior to the comparator IIV3 for all three influenza vaccine strains. Rates of solicited and unsolicited vaccine-related adverse events were similar between the two vaccine groups. These results demonstrated that Shz-IIV3 was as immunogenic and safe in adults as a comparator Chinese IIV3, and support the continued use of Shz-IIV3 in China.

The burden of influenza-associated respiratory hospitalizations in Bhutan, 2015-2016

BACKGROUND

Influenza burden estimates help provide evidence to support influenza prevention and control programs. In this study, we estimated influenza-associated respiratory hospitalization rates in Bhutan, a country considering influenza vaccine introduction.

METHODS

Using real-time reverse transcription-polymerase chain reaction laboratory results from severe acute respiratory infection (SARI) surveillance, we estimated the proportion of respiratory hospitalizations attributable to influenza each month among patients aged <5, 5-49, and ≥50 years in six Bhutanese districts for 2015 and 2016. We divided the sum of the monthly influenza-attributed hospitalizations by the total of the six district populations to generate age-specific rates for each year.

RESULTS

In 2015, 10% of SARI patients tested positive for influenza (64/659) and 18% tested positive (129/736) in 2016. The incidence of influenza-associated hospitalizations among all age groups was 50/100 000 persons (95% confidence interval [CI]: 45-55) in 2015 and 118/100 000 persons (95% CI: 110-127) in 2016. The highest rates were among children <5 years: 182/100 000 (95% CI: 153-210) in 2015 and 532/100 000 (95% CI: 473-591) in 2016. The second highest influenza-associated hospitalization rates were among adults ≥50 years: 110/100 000 (95% CI: 91-130) in 2015 and 193/100 000 (95% CI: 165-221) in 2016.

CONCLUSIONS

Influenza viruses were associated with a substantial burden of severe illness requiring hospitalization especially among children and older adults. These findings can be used to understand the potential impact of seasonal influenza vaccination in these age groups.

Expanding severe acute respiratory infection (SARI) surveillance beyond influenza: The process and data from 1 year of implementation in Vietnam

BACKGROUND

In 2016, as a component of the Global Health Security Agenda, the Vietnam Ministry of Health expanded its existing influenza sentinel surveillance for severe acute respiratory infections (SARI) to include testing for 7 additional viral respiratory pathogens. This article describes the steps taken to implement expanded SARI surveillance in Vietnam and reports data from 1 year of expanded surveillance.

METHODS

The process of expanding the suite of pathogens for routine testing by real-time reverse transcriptase-polymerase chain reaction (rRT-PCR) included laboratory trainings, procurement/distribution of reagents, and strengthening and aligning SARI surveillance epidemiology practices at sentinel sites and regional institutes (RI).

RESULTS

Surveillance data showed that of 4003 specimens tested by the RI laboratories, 20.2% (n = 810) were positive for influenza virus. Of the 3193 influenza-negative specimens, 41.8% (n = 1337) were positive for at least 1 non-influenza respiratory virus, of which 16.2% (n = 518), 13.4% (n = 428), and 9.6% (n = 308) tested positive for respiratory syncytial virus, rhinovirus, and adenovirus, respectively.

CONCLUSIONS

The Government of Vietnam has demonstrated that expanding respiratory viral surveillance by strengthening and building upon an influenza platform is feasible, efficient, and practical.

Invasive Streptococcus pneumoniae infection among hospitalized patients in Jingzhou city, China, 2010-2012

BACKGROUND

Streptococcus pneumoniae (Sp) is a leading cause of bacterial pneumonia, meningitis, and sepsis and a major source of morbidity and mortality worldwide. Invasive pneumococcal disease (IPD) is defined as isolation of Sp from a normally sterile site, including blood or cerebrospinal fluid. The aim of this study is to describe outcomes as well as clinical and epidemiological characteristics of hospitalized IPD case patients in central China.

METHODS

We conducted surveillance for IPD among children and adults from April 5, 2010 to September 30, 2012, in four major hospitals in Jingzhou City, Hubei Province. We collected demographic, clinical, and outcome data for all enrolled hospitalized patients with severe acute respiratory infection (SARI) or meningitis, and collected blood, urine, and cerebrospinal fluid (CSF) for laboratory testing for Sp infections. Collected data were entered into Epidata software and imported into SPSS for analysis.

RESULTS

We enrolled 22,375 patients, including 22,202 (99%) with SARI and 173 (1%) with meningitis. One hundred and eighteen (118, 3%) with either SARI or meningitis were Sp positive, 32 (0.8%) from blood/CSF culture, and 87 (5%) from urine antigen testing. Of those 118 patients, 57% were aged ≥65 years and nearly 100% received antibiotics during hospitalization. None were previously vaccinated with 7-valent pneumococcal conjugate vaccine (PCV 7), 23-valent pneumococcal polysaccharide vaccine, or seasonal influenza vaccine. The main serotypes identified were 14, 12, 3, 1, 19F, 4, 5, 9V, 15 and 18C, corresponding to serotype coverage rates of 42%, 63%, and 77% for PCV7, PCV10, and PCV13, respectively.

CONCLUSIONS

Further work is needed to expand access to pneumococcal vaccination in China, both among children and potentially among the elderly, and inappropriate use of antibiotics is a widespread and serious problem in China.

Global Disease Detection-Achievements in Applied Public Health Research, Capacity Building, and Public Health Diplomacy, 2001-2016

The Centers for Disease Control and Prevention has established 10 Global Disease Detection (GDD) Program regional centers around the world that serve as centers of excellence for public health research on emerging and reemerging infectious diseases. The core activities of the GDD Program focus on applied public health research, surveillance, laboratory, public health informatics, and technical capacity building. During 2015-2016, program staff conducted 205 discrete projects on a range of topics, including acute respiratory illnesses, health systems strengthening, infectious diseases at the human-animal interface, and emerging infectious diseases. Projects incorporated multiple core activities, with technical capacity building being most prevalent. Collaborating with host countries to implement such projects promotes public health diplomacy. The GDD Program continues to work with countries to strengthen core capacities so that emerging diseases can be detected and stopped faster and closer to the source, thereby enhancing global health security.

Literature review of the epidemiology of influenza B disease in 15 countries in the Asia-Pacific region

Influenza control strategies focus on the use of trivalent influenza vaccines containing two influenza A virus subtypes and one of the two circulating influenza type B lineages (Yamagata or Victoria). Mismatches between the vaccine B lineage and the circulating lineage have been regularly documented in many countries, including those in the Asia‐Pacific region. We conducted a literature review with the aim of understanding the relative circulation of influenza B viruses in Asia‐Pacific countries. PubMed and Western Pacific Region Index Medicus were searched for relevant articles on influenza type B published since 1990 in English language for 15 Asia‐Pacific countries. Gray literature was also accessed. From 4834 articles identified, 121 full‐text articles were analyzed. Influenza was reported as an important cause of morbidity in the Asia‐Pacific region, affecting all age groups. In all 15 countries, influenza B was identified and associated with between 0% and 92% of laboratory‐confirmed influenza cases in any one season/year. Influenza type B appeared to cause more illness in children aged between 1 and 10 years than in other age groups. Epidemiological data for the two circulating influenza type B lineages remain limited in several countries in the Asia‐Pacific, although the co‐circulation of both lineages was seen in countries where strain surveillance data were available. Mismatches between circulating B lineages and vaccine strains were observed in all countries with available data. The data suggest that a shift from trivalent to quadrivalent seasonal influenza vaccines could provide additional benefits by providing broader protection.

Using a hospital admission survey to estimate the burden of influenza-associated severe acute respiratory infection in one province of Cambodia-methods used and lessons learned

Background

Understanding the burden of influenza‐associated severe acute respiratory infection (SARI) is important for setting national influenza surveillance and vaccine priorities. Estimating influenza‐associated SARI rates requires hospital‐based surveillance data and a population‐based denominator, which can be challenging to determine.

Objectives

We present an application of the World Health Organization's recently developed manual (WHO Manual) including hospital admission survey (HAS) methods for estimating the burden of influenza‐associated SARI, with lessons learned to help others calculate similar estimates.

Methods

Using an existing SARI surveillance platform in Cambodia, we counted influenza‐associated SARI cases during 2015 at one sentinel surveillance site in Svay Rieng Province. We applied WHO Manual‐derived methods to count respiratory hospitalizations at all hospitals within the catchment area, where 95% of the sentinel site case‐patients resided. We used HAS methods to adjust the district‐level population denominator for the sentinel site and calculated the incidence rate of influenza‐associated SARI by dividing the number of influenza‐positive SARI infections by the adjusted population denominator and multiplying by 100 000. We extrapolated the rate to the provincial population to derive a case count for 2015. We evaluated data sources, detailed steps of implementation, and identified lessons learned.

Results

We estimated an adjusted influenza‐associated 2015 SARI rate of 13.5/100 000 persons for the catchment area of Svay Rieng Hospital and 77 influenza‐associated SARI cases in Svay Rieng Province after extrapolation.

Conclusions

Methods detailed in the WHO Manual and operationalized successfully in Cambodia can be used in other settings to estimate rates of influenza‐associated SARI.

Comparing the similarity and difference of three influenza surveillance systems in China

Three main surveillance systems (laboratory-confirmed, influenza-like illness (ILI) and nationwide Notifiable Infectious Diseases Reporting Information System (NIDRIS)) have been used for influenza surveillance in China. However, it is unclear which surveillance system is more reliable in developing influenza early warning system based on surveillance data. This study aims to evaluate the similarity and difference of the three surveillance systems and provide practical knowledge for improving the effectiveness of influenza surveillance. Weekly influenza data for the three systems were obtained from March 2010 to February 2015. Spearman correlation and time series seasonal decomposition were used to assess the relationship between the three surveillance systems and to explore seasonal patterns and characteristics of influenza epidemics in Gansu, China. Our results showed influenza epidemics appeared a single-peak around January in all three surveillance systems. Time series seasonal decomposition analysis demonstrated a similar seasonal pattern in the three systems, while long-term trends were observed to be different. Our research suggested that a combination of the NIDRIS together with ILI and laboratory-confirmed surveillance is an informative, comprehensive way to monitor influenza transmission in Gansu, China. These results will provide a useful information for developing influenza early warning systems based on influenza surveillance data.

Innovations in adult influenza vaccination in China, 2014-2015: Leveraging a chronic disease management system in a community-based intervention

Objectives: To evaluate a community-based intervention that leveraged the non-communicable disease management system to increase seasonal influenza vaccination coverage among older adults in Ningbo, China. Methods: From October 2014 – March 2015, we piloted the following on one street in Ningbo, China: educating community healthcare workers (C-HCWs) about influenza and vaccination; requiring C-HCWs to recommend influenza vaccination to older adults during routine chronic disease follow-up; and opening 14 additional temporary vaccination clinics. We selected a non-intervention street for comparison pre- and post-intervention vaccine coverage. In April 2016, we interviewed a random sample of unvaccinated older adults on the intervention street to ask why they remained unvaccinated. Results: Pre-intervention influenza vaccine coverage among adults aged 60 years and older on both streets was 0.3%. Post-intervention, coverage among adults 60 years and older was 19% (1338/7013) on the intervention street and 0.4% (20/5500) on the non-intervention street (p<0.01). Among vaccinated older adults, 98% reported their main reason for vaccination was receiving a C-HCW's recommendation, 90% were vaccinated at temporary vaccination clinics, and 53% paid for vaccine (10 USD) out-of-pocket. Reasons for not getting vaccinated among 150 unvaccinated adults (response rate = 75%) included: good health (39%); not trusting C-HCWs' recommendations (24%); not knowing where to get vaccinated (17%); and not wanting to pay (9%). Conclusions: Recommending influenza vaccination within a non-communicable disease management system, combined with adding vaccination sites, increased vaccine coverage among older adults in Ningbo, China.

Prevention and treatment of respiratory viral infections: Presentations on antivirals, traditional therapies and host-directed interventions at the 5th ISIRV Antiviral Group conference

The International Society for Influenza and other Respiratory Virus Diseases held its 5th Antiviral Group (isirv-AVG) Conference in Shanghai, China, in conjunction with the Shanghai Public Health Center and Fudan University from 14-16 June 2017. The three-day programme encompassed presentations on some of the clinical features, management, immune responses and virology of respiratory infections, including influenza A(H1N1)pdm09 and A(H7N9) viruses, MERS-CoV, SARS-CoV, adenovirus Type 80, enterovirus D68, metapneumovirus and respiratory syncytial virus (RSV). Updates were presented on several therapeutics currently in clinical trials, including influenza polymerase inhibitors pimodivir/JNJ6362387, S033188, favipiravir, monoclonal antibodies MHAA45449A and VIS410, and host directed strategies for influenza including nitazoxanide, and polymerase ALS-008112 and fusion inhibitors AK0529, GS-5806 for RSV. Updates were also given on the use of the currently licensed neuraminidase inhibitors. Given the location in China, there were also presentations on the use of Traditional Chinese Medicines. Following on from the previous conference, there were ongoing discussions on appropriate endpoints for severe influenza in clinical trials from regulators and clinicians, an issue which remains unresolved. The aim of this conference summary is to provide information for not only conference participants, but a detailed referenced review of the current status of clinical trials, and pre-clinical development of therapeutics and vaccines for influenza and other respiratory diseases for a broader audience.

Seasonal pattern of influenza activity in a subtropical city, China, 2010-2015

Influenza seasonality study is critical for policy-makers to choose an optimal time for influenza vaccination campaign, especially for subtropical regions where influenza seasonality and periodicity are unclear. In this study, we explored the seasonality and periodicity of influenza in Hefei, China during 2010 to 2015 using five proxies originated from three data sources of clinical surveillance of influenza-like illness (ILI), laboratory surveillance of influenza and death registration of pneumonia and influenza. We combined both wavelets analysis and de-linear-trend regression with Fourier harmonic terms to estimate seasonal characteristics of epidemic phase, peak time, amplitude, ratio of dominant seasonality. We found both annual cycle of influenza epidemics peaking in December-February and semi-annual cycle peaking in December-February and June-July in subtropical city Hefei, China. Compared to proxies developed by ILI and death registration data separately, influenza proxies incorporated laboratory surveillance data performed better seasonality and periodicity, especially in semi-annual periodicity in Hefei. Proxy of ILI consultation rate showed more timeliness peak than other proxies, and could be useful in developing the early warning model for influenza epidemics. Our study suggests to integrate clinical and laboratory surveillance of influenza for future influenza seasonality studies in subtropical regions.

The impact of influenza on the health related quality of life in China: an EQ-5D survey

BACKGROUND

Influenza causes considerable morbidity and mortality in China, but its impact on the health-related quality of life (HRQoL) has not been previously measured.

METHODS

We conducted a retrospective telephone survey to assess the impact of influenza on the HRQoL among outpatients and inpatients using the EuroQoL EQ-5D-3 L instrument. Participants were individuals with laboratory-confirmed influenza infection registered by the National Influenza-like-illness Surveillance Network in 2013.

RESULTS

We interviewed 839 of 11,098 eligible influenza patients. After excluding those who were unable to complete the HRQoL for the registered influenza episode, 778 patients were included in the analysis. Both outpatients (n = 529) and inpatients (n = 249) most commonly reported problems with pain/discomfort (71.8% of outpatients and 71.9% of inpatients) and anxiety/depression (62.0% of outpatients and 75.1% of inpatients). For individual influenza outpatients, the mean health utility was 0.6142 (SD 0.2006), and the average quality adjusted life days (QALD) loss was 1.62 (SD 1.84) days. The HRQoL of influenza inpatients was worse (mean health utility 0.5851, SD 0.2197; mean QALD loss 3.51 days, SD 4.25) than that of outpatients (p < 0.05). The presence of underlying medical conditions lowered the HRQoL for both outpatients and inpatients (p < 0.05).

CONCLUSIONS

Influenza illness had a substantial impact on HRQoL. QALD loss due to an acute influenza episode in younger children was comparable to that due to enterovirus A71-associated hand, foot and mouth disease. Our findings are key inputs into disease burden estimates and cost-effectiveness evaluations of influenza-related interventions in China.

Incidence of laboratory-confirmed influenza disease among infants under 6 months of age: a systematic review

OBJECTIVES

The aim of this systematic review was to assess incidence rates of laboratory-confirmed influenza (LCI) outcomes among infants under 6 months of age.

DESIGN

Systematic literature search and review of indexed studies in PubMed, EMBASE, the Cochrane Library and CINAHL Plus from inception to 19 April 2017.

SETTING

Population-based estimates from community or hospital settings.

PARTICIPANTS

Infants under 6 months of age.

PRIMARY AND SECONDARY OUTCOME MEASURES

LCI illness in ambulatory care settings, LCI hospitalisation, LCI intensive care unit admission and LCI death. Only studies with population-based incidence data were included.

RESULTS

We identified 27 primary studies, 11 of which were from the USA, four were from other non-US high-income settings and the remaining were from lower-middle-income or upper-middle-income countries. Most studies (n=23) assessed incidence of LCI hospitalisation, but meta-analysis to pool study-specific rates was not possible due to high statistical and methodological heterogeneity. Among US studies, the reported incidence of LCI hospitalisation ranged from 9.3 to 91.2 per 10 000 infants under 6 months for seasonal influenza, while the only US-based estimate for pandemic H1N1 influenza was 20.2 per 10 000 infants. Reported rates for LCI hospitalisation for seasonal influenza from other countries ranged from 6.2 to 73.0 per 10 000 infants under 6 months, with the exception of one study with an estimated rate of 250 per 10 000 infants. No events were reported in five of the nine studies that evaluated LCI death among infants under 6 months.

CONCLUSION

Our review of published studies found limited data on LCI outcomes for infants under 6 months, particularly from non-US settings. Globally representative and reliable incidence data are necessary to fully evaluate influenza disease burden and the potential impact of maternal influenza immunisation programme on morbidity and mortality in young infants.

Influenza epidemiology and immunization during pregnancy: Final report of a World Health Organization working group

From 2014 to 2017, the World Health Organization convened a working group to evaluate influenza disease burden and vaccine efficacy to inform estimates of maternal influenza immunization program impact. The group evaluated existing systematic reviews and relevant primary studies, and conducted four new systematic reviews. There was strong evidence that maternal influenza immunization prevented influenza illness in pregnant women and their infants, although data on severe illness prevention were lacking. The limited number of studies reporting influenza incidence in pregnant women and infants under six months had highly variable estimates and underrepresented low- and middle-income countries. The evidence that maternal influenza immunization reduces the risk of adverse birth outcomes was conflicting, and many observational studies were subject to substantial bias. The lack of scientific clarity regarding disease burden or magnitude of vaccine efficacy against severe illness poses challenges for robust estimation of the potential impact of maternal influenza immunization programs.

Drug resistance in influenza A virus: the epidemiology and management

Influenza A virus (IAV) is the sole cause of the unpredictable influenza pandemics and deadly zoonotic outbreaks and constitutes at least half of the cause of regular annual influenza epidemics in humans. Two classes of anti-IAV drugs, adamantanes and neuraminidase (NA) inhibitors (NAIs) targeting the viral components M2 ion channel and NA, respectively, have been approved to treat IAV infections. However, IAV rapidly acquired resistance against both classes of drugs by mutating these viral components. The adamantane-resistant IAV has established itself in nature, and a majority of the IAV subtypes, especially the most common H1N1 and H3N2, circulating globally are resistant to adamantanes. Consequently, adamantanes have become practically obsolete as anti-IAV drugs. Similarly, up to 100% of the globally circulating IAV H1N1 subtypes were resistant to oseltamivir, the most commonly used NAI, until 2009. However, the 2009 pandemic IAV H1N1 subtype, which was sensitive to NAIs and has now become one of the dominant seasonal influenza virus strains, has replaced the pre-2009 oseltamivir-resistant H1N1 variants. This review traces the epidemiology of both adamantane- and NAI-resistant IAV subtypes since the approval of these drugs and highlights the susceptibility status of currently circulating IAV subtypes to NAIs. Further, it provides an overview of currently and soon to be available control measures to manage current and emerging drug-resistant IAV. Finally, this review outlines the research directions that should be undertaken to manage the circulation of IAV in intermediate hosts and develop effective and alternative anti-IAV therapies.