Assessing interventions to encourage primary care health workers to recommend influenza vaccination and the impact on vaccination uptake for persons with Non-Communicable diseases in China.

BACKGROUND: Influenza vaccination coverage is low among persons with non-communicable diseases (NCDs) in China. Chinese health workers (HWs) do not routinely recommend influenza vaccination despite evidence that recommendations increase vaccine uptake. This study aims to assess whether interventions increased primary care HWs' recommendation for influenza vaccination and measure their impact on influenza vaccine uptake in persons with NCDs. METHODS: We conducted a cluster randomized controlled study in public primary healthcare clinics in Hubei from November 2018 through April 2019. In the intervention clinics, primary care HWs received training on the benefits of influenza vaccination and were asked to recommend influenza vaccine in routine primary healthcare for persons with NCDs. In the control clinics, primary care HWs did not receive training and provided standard services. We conducted questionnaire surveys before and after the intervention to collect information about recommendations made and receipt of influenza vaccines. RESULTS: A total of 896 primary care HWs and 4552 persons with NCDs were included. After intervention, a higher percentage of HWs recommended influenza vaccines in intervention clinics compared to control clinics. Vaccinated primary care HWs were more likely to recommend vaccination. Persons with NCDs reported higher influenza vaccination coverage in intervention than control clinics, and primary care HWs' recommendation increased vaccination uptake among persons with NCDs. CONCLUSIONS: Vaccinated primary care HWs were more likely to recommend influenza vaccination than unvaccinated HWs. Promoting primary care HWs' vaccination and encouraging them to recommend influenza vaccination during routine primary healthcare could increase influenza vaccine receipt among persons with NCDs. Registration number ChiCTR2200067140.

Mild and asymptomatic influenza B virus infection among unvaccinated pregnant persons: Implication for effectiveness of non-pharmaceutical intervention and vaccination to prevent influenza.

BACKGROUND: We estimated symptomatic and asymptomatic influenza infection frequency in community-dwelling unvaccinated pregnant persons to inform risk communication. METHODS: We collected residue sera from multiple antenatal-care blood draws during October 2016-April 2017. We determined influenza infection as seroconversion with ≥ 4-fold rise in antibody titers between any two serum samples by improved hemagglutinin-inhibition assay including ether-treated B antigens. The serology data were linked to the results of nuclei acid testing (rRT-PCR) based on acute respiratory illness (ARI) surveillance. RESULTS: Among all participants, 43 %(602/1384) demonstrated serology and/or rRT-PCR evidenced infection, and 44 %(265/602) of all infections were asymptomatic. ARI-associated rRT-PCR testing identified only 10 %(61/602) of total infections. Only 1 %(5/420) of the B Victoria cases reported ARI and had a rRT-PCR positive result, compared with 33 %(54/165) of the H3N2 cases. Among influenza ARI cases with multiple serum samples, 19 %(11/58) had seroconversion to a different subtype prior to the illness. CONCLUSIONS: The incidence of influenza B infection in unvaccinated pregnant persons is under-estimated substantially. Non-pharmaceutical intervention may have suboptimal effectiveness in preventing influenza B transmission due to the less clinical manifestation compared to influenza A. The findings support maternal influenza vaccination to protect pregnant persons and reduce consequent household transmission.

Incidence rates of influenza illness during pregnancy in Suzhou, China, 2015-2018.

BACKGROUND: Data on influenza incidence during pregnancy in China are limited. METHODS: From October 2015 to September 2018, we conducted active surveillance for acute respiratory illness (ARI) among women during pregnancy. Nurses conducted twice weekly phone and text message follow-up upon enrollment until delivery to identify new episodes of ARI. Nasal and throat swabs were collected ≤10 days from illness onset to detect influenza. RESULTS: In total, we enrolled 18 724 pregnant women median aged 28 years old, 37% in first trimester, 48% in second trimester, and 15% in third trimester, with seven self-reported influenza vaccination during pregnancy. In the 18-week epidemic period during October 2015 to September 2016, influenza incidence was 0.7/100 person-months (95% CI: 0.5-0.9). In the cumulative 29-week-long epidemic during October 2016 to September 2017, influenza incidence was 1.0/100 person-months (95% CI: 0.8-1.2). In the 11-week epidemic period during October 2017 to September 2018, influenza incidence was 2.1/100 person-months (95% CI: 1.9-2.4). Influenza incidence was similar by trimester. More than half of the total influenza illnesses had no elevated temperature and cough. Most influenza-associated ARIs were mild, and <5.1% required hospitalization. CONCLUSIONS: Influenza illness in all trimesters of pregnancy was common. These data may help inform decisions regarding the use of influenza vaccine to prevent influenza during pregnancy.

Use of public data to describe COVID-19 contact tracing in Hubei Province and non-Hubei provinces in China between 20 January and 29 February 2020.

OBJECTIVE: Contact tracing has been used in China and several other countries in the WHO Western Pacific Region as part of the COVID-19 response. We describe COVID-19 cases and the number of contacts traced and quarantined per case as part of COVID-19 emergency public health response activities in China. METHODS: We abstracted publicly available, online aggregated data published in daily COVID-19 situational reports by China's National Health Commission and provincial health commissions between 20 January and 29 February 2020. The number of new contacts traced by report date was computed as the difference between total contacts traced in consecutive reports. A proxy for the number of contacts traced per case was computed as the number of new contacts traced divided by the number of new cases. RESULTS: During the study period, China reported 80 968 new COVID-19 cases and 659 899 contacts. In Hubei Province, there were 67 608 cases and 264 878 contacts, representing 83% and 40% of the total, respectively. Non-Hubei provinces reported tracing 1.5 times more contacts than Hubei Province; the weekly number of contacts traced per case was also higher in non-Hubei provinces than in Hubei Province and increased from 17.2 in epidemiological week 4 to 115.7 in epidemiological week 9. DISCUSSION: More contacts per case were reported from areas and periods with lower COVID-19 case counts. With other non-pharmaceutical interventions used in China, contact tracing and quarantining large numbers of potentially infected contacts probably contributed to reducing SARS-CoV-2 transmission.

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.

Review of the status and challenges associated with increasing influenza vaccination coverage among pregnant women in China.

Influenza vaccination coverage in pregnant women in China remains low. In this review, we first provide an overview of the evidence for the use of influenza vaccination during pregnancy. Second, we discuss influenza vaccination policy and barriers to increased seasonal influenza vaccination coverage in pregnant women in China. Third, we provide case studies of successes and challenges of programs for increasing seasonal influenza vaccination in pregnant women from other parts of Asia with lessons learned for China. Finally, we assess opportunities and challenges for increasing influenza vaccination coverage among pregnant women in China.

Dose effect of influenza vaccine on protection against laboratory-confirmed influenza illness among children aged 6 months to 8 years of age in southern China, 2013/14-2015/16 seasons: a matched case-control study.

Background We conducted a matched case-control study in China during the 2013/14-2015/16 influenza seasons to estimate influenza vaccine effectiveness (VE) by dose among children aged 6 months to 8 years.Methods Cases were laboratory-confirmed influenza infections identified through the influenza-like illness sentinel surveillance network in Guangzhou. Age- and sex-matched community controls were randomly selected through the expanded immunization program database. We defined priming as receipt of ≥1 dose of influenza vaccine during the immediate prior season.Results In total, 4,185 case-control pairs were analyzed. Among children 6-35 months, VE for current season dose(s) across the three seasons during 2013/14-2015/16 were 59% (95% Confidence Interval: 44-71%), 12% (-11%,30%), 54% (32-69%); among unprimed children 6-35 months, VE for 1 vs 2 current season doses were 45% (8-67%) vs 65% (46-78%), -2% (-53%,32%) vs 19% (-11%,40%), and 37% (-24%,68%) vs 61% (32-78%). Among children aged 3-8 years, VE for current season dose(s) across study seasons were 62% (36-78%), 43% (22-58%), 32% (1-53%). VE for unprimed children receiving 1 dose only in current season was insignificant or lower than among all children.Conclusion Findings support utility of providing second dose ("booster dose") of seasonal influenza vaccine to unprimed children aged 6-35 months, and the need to study further dose effect of a booster dose among unprimed children aged 3-8 years in China.

Lessons from an active surveillance pilot to assess the pneumonia of unknown etiology surveillance system in China, 2016: the need to increase clinician participation in the detection and reporting of emerging respiratory infectious diseases.

BACKGROUND: We sought to assess reporting in China's Pneumonia of Unknown Etiology (PUE) passive surveillance system for emerging respiratory infections and to identify ways to improve the PUE surveillance system's detection of respiratory infections of public health significance. METHODS: From February 29-May 29, 2016, we actively identified and enrolled patients in two hospitals with acute respiratory infections (ARI) that met all PUE case criteria. We reviewed medical records for documented exposure history associated with respiratory infectious diseases, collected throat samples that were tested for seasonal and avian influenza, and interviewed clinicians regarding reasons for reporting or not reporting PUE cases. We described and analyzed the proportion of PUE cases reported and clinician awareness of and practices related to the PUE system. RESULTS: Of 2619 ARI admissions in two hospitals, 335(13%) met the PUE case definition; none were reported. Of 311 specimens tested, 18(6%) were seasonal influenza virus-positive; none were avian influenza-positive. < 10% PUE case medical records documented whether or not there were exposures to animals or others with respiratory illness. Most commonly cited reasons for not reporting cases were no awareness of the PUE system (76%) and not understanding the case definition (53%). CONCLUSIONS: Most clinicians have limited awareness of and are not reporting to the PUE system. Exposures related to respiratory infections are rarely documented in medical records. Increasing clinicians' awareness of the PUE system and including relevant exposure items in standard medical records may increase reporting.

A ten-year China-US laboratory collaboration: improving response to influenza threats in China and the world, 2004-2014.

The emergence of severe acute respiratory syndrome (SARS) underscored the importance of influenza detection and response in China. From 2004, the Chinese National Influenza Center (CNIC) and the United States Centers for Disease Control and Prevention (USCDC) initiated Cooperative Agreements to build capacity in influenza surveillance in China.From 2004 to 2014, CNIC and USCDC collaborated on the following activities: 1) developing human technical expertise in virology and epidemiology in China; 2) developing a comprehensive influenza surveillance system by enhancing influenza-like illness (ILI) reporting and virological characterization; 3) strengthening analysis, utilization and dissemination of surveillance data; and 4) improving early response to influenza viruses with pandemic potential.Since 2004, CNIC expanded its national influenza surveillance and response system which, as of 2014, included 408 laboratories and 554 sentinel hospitals. With support from USCDC, more than 2500 public health staff from China received virology and epidemiology training, enabling > 98% network laboratories to establish virus isolation and/or nucleic acid detection techniques. CNIC established viral drug resistance surveillance and platforms for gene sequencing, reverse genetics, serologic detection, and vaccine strains development. CNIC also built a bioinformatics platform to strengthen data analysis and utilization, publishing weekly on-line influenza surveillance reports in English and Chinese. The surveillance system collects 200,000-400,000 specimens and tests more than 20,000 influenza viruses annually, which provides valuable information for World Health Organization (WHO) influenza vaccine strain recommendations. In 2010, CNIC became the sixth WHO Collaborating Centre for Influenza. CNIC has strengthened virus and data sharing, and has provided training and reagents for other countries to improve global capacity for influenza control and prevention.The collaboration's successes were built upon shared mission and values, emphasis on long-term capacity development and sustainability, and leadership commitment.

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.

Cohort profile: China respiratory illness surveillance among pregnant women (CRISP), 2015-2018.

PURPOSE: We established the China Respiratory Illness Surveillance among Pregnant women (CRISP) to conduct active surveillance for influenza-associated respiratory illness during pregnancy in China from 2015 to 2018. Among annual cohorts of pregnant women, we assess the incidence of acute respiratory illness (ARI), influenza-like illness (ILI), laboratory-confirmed influenza virus infection and the seroconversion proportion during the winter influenza season. We also plan to examine the effect of influenza virus infection on adverse pregnancy, delivery and infant health outcomes with cumulative data from the three annual cohorts. PARTICIPANTS: Cohort nurses enrol pregnant women in different trimesters of pregnancy from prenatal care facilities in Suzhou, Jiangsu Province, eastern China. Pregnant women who plan to deliver in the study facilities are eligible. Pregnant women who are seeking care for anything other than routine prenatal care, such as confirmation of low progesterone and threatened miscarriage, are excluded. At enrolment, study nurses collect baseline information on demographics, education-level attained, underlying medical conditions, seasonal influenza vaccination receipt, risk factors for influenza infection, gravidity and parity and contact information. For each participant, cohort nurses conduct twice weekly follow-up contacts, one phone call and one WeChat message (free instant messaging), from the time of enrolment until delivery or termination of pregnancy. During follow-up, study nurses ask about symptoms, timing and characteristics of ARI, healthcare-seeking behaviour and medications taken for participants reporting respiratory illness since the last contact. In addition, we collect combined nasal and throat swabs for identified ARI to test for influenza viruses. We collect paired sera before and after the influenza season. Active respiratory illness surveillance and seroinfection data during pregnancy of participants are linked to their medical record and the Suzhou Maternal Child Information System for detailed information on clinical treatment for respiratory illness, pregnancy, delivery and infant health outcomes. FINDINGS TO DATE: In 2015-2016, of 4915 pregnant women approached, 192 (4%) refused to participate, 91 (2%) were ineligible because they did not plan to deliver in one of the study hospitals or because their visit was for anything other than routine prenatal care and 4632 (94%) were enrolled, 46% during their first trimester of pregnancy (range 5-12 weeks), 48% during the second trimester (range 13-27 weeks) and 6% during the third trimester (range 28-37 weeks). The median age of the enrollees was 27 years (range 16-45) and two (0.04%, 95% CI 0.01% to 0.17%) reported influenza vaccination in the previous 12 months before pregnancy, while zero reported influenza vaccination in the previous 12 months during pregnancy. During the observation time of 648 518 person-days, 1355 ARI episodes were identified. Among 1127 swabs collected (for 83% of all ARIs), 68 (6%) tested positive for influenza virus, for a laboratory-confirmed influenza incidence of 0.31 (95% CI 0.25 to 0.40) per 100 person-months during pregnancy in the study cohort. FUTURE PLANS: Results will be used to describe influenza disease burden in this population to model potential numbers of influenza illnesses averted if influenza vaccination coverage were increased and to support enhanced influenza prevention and control strategies among pregnant women in China. We also plan to enrol and follow three cohorts of pregnant women over three influenza seasons during 2015-2018 which will allow an analysis of the effect of influenza virus infection during pregnancy on adverse pregnancy, delivery and infant outcomes.

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.

Influenza-associated paediatric respiratory hospitalizations in China, 1996-2012: a systematic analysis.

BACKGROUND: The World Health Organization recommends that children aged ≥ 6 months be vaccinated against influenza. Influenza vaccination policies depend on the evidence of the burden of influenza, yet few national data on influenza-associated severe outcomes among children exist in China. METHODS: We conducted a systematic review of articles published from 1996 to 2012 on laboratory-confirmed, influenza-associated paediatric respiratory hospitalizations in China. We extracted data and stratified the percentage of samples testing positive for influenza by age group (< 2, < 5 and < 18 years old); case definition; test methods; and geographic location. The pooled percentage of samples testing positive for influenza was estimated with a random effects regression model. RESULTS: Influenza was associated with 8.8% of respiratory hospitalizations among children aged < 18 years, ranging from 7.0% (95% confidence interval: 4.2-9.8%) in children aged < 2 years to 8.9% (95% confidence interval: 6.8-11%) in children aged < 5 years. The percentage of samples testing positive for influenza was consistently higher among studies with data from children aged < 5 years and < 18 years than those restricted only to children aged < 2 years; the percentages were higher in Northern China than Southern China. DISCUSSION: Influenza is an important cause of paediatric respiratory hospitalizations in China. Influenza vaccination of school-aged children could prevent substantial influenza-associated illness, including hospitalizations, in China.

Potential impact of B lineage mismatch on trivalent influenza vaccine effectiveness during the 2015-2016 influenza season among nursery school children in Suzhou, China.

BACKGROUND: We actively followed a cohort of nursery school children in Suzhou, China to assess the impact of vaccination with trivalent influenza vaccine on the prevention of influenza like illness (ILI). METHODS: We enrolled children aged 36 to 72 months from 13 nursery schools in Suzhou starting two weeks after vaccination during October 2015-February 2016. Every school-day, teachers reported the names of students with ILI to study clinicians, who collected the student's nasopharyngeal swab or throat swab, either at a study clinic or the child's home. Swabs were sent to the Suzhou Center for Disease Control and Prevention's laboratory for influenza testing by RT-PCR. RESULTS: In total, 3278 children were enrolled; 83 (3%) were lost to follow-up, while 3195 (vaccinated: 1492, unvaccinated: 1703) were followed for 24 weeks. During the study, 40 samples tested positive; 17 in the vaccinated (B Victoria: 12; A(H1N1)pdm09: 5) and 23 in the unvaccinated group (B Victoria: 10; B Yamagata: 2; A(H1N1)pdm09: 11). The VE estimates were: 16% overall (95%CI:-58%,56%), 48% (-47%,84%) for influenza A(H1N1)pdm09, 43% (-650%,98%) for influenza B Yamagata, and -37% (-227%,42%) for influenza B Victoria. Data were analyzed by vaccinated and unvaccinated groups based on enrollees' vaccination records. CONCLUSIONS: The VE for A(H1N1)pdm09 was moderate but not significant. Mismatching of B lineage may have compromised trivalent influenza vaccine effectiveness during the 2015-2016 influenza season among nursery school children in Suzhou, China. Additional larger studies are warranted to inform policy related to quadrivalent influenza vaccine licensure in China in the future.

Clusters of Human Infections With Avian Influenza A(H7N9) Virus in China, March 2013 to June 2015.

Multiple clusters of human infections with novel avian influenza A(H7N9) virus have occurred since the virus was first identified in spring 2013. However, in many situations it is unclear whether these clusters result from person-to-person transmission or exposure to a common infectious source. We analyzed the possibility of person-to-person transmission in each cluster and developed a framework to assess the likelihood that person-to-person transmission had occurred. We described 21 clusters with 22 infected contact cases that were identified by the Chinese Center for Disease Control and Prevention from March 2013 through June 2015. Based on detailed epidemiological information and the timing of the contact case patients' exposures to infected persons and to poultry during their potential incubation period, we graded the likelihood of person-to-person transmission as probable, possible, or unlikely. We found that person-to-person transmission probably occurred 12 times and possibly occurred 4 times; it was unlikely in 6 clusters. Probable nosocomial transmission is likely to have occurred in 2 clusters. Limited person-to-person transmission is likely to have occurred on multiple occasions since the H7N9 virus was first identified. However, these transmission events represented a small fraction of all identified cases of H7N9 human infection, and sustained person-to-person transmission was not documented.

Update: Increase in Human Infections with Novel Asian Lineage Avian Influenza A(H7N9) Viruses During the Fifth Epidemic - China, October 1, 2016-August 7, 2017.

Among all influenza viruses assessed using CDC's Influenza Risk Assessment Tool (IRAT), the Asian lineage avian influenza A(H7N9) virus (Asian H7N9), first reported in China in March 2013,* is ranked as the influenza virus with the highest potential pandemic risk (1). During October 1, 2016-August 7, 2017, the National Health and Family Planning Commission of China; CDC, Taiwan; the Hong Kong Centre for Health Protection; and the Macao CDC reported 759 human infections with Asian H7N9 viruses, including 281 deaths, to the World Health Organization (WHO), making this the largest of the five epidemics of Asian H7N9 infections that have occurred since 2013 (Figure 1). This report summarizes new viral and epidemiologic features identified during the fifth epidemic of Asian H7N9 in China and summarizes ongoing measures to enhance pandemic preparedness. Infections in humans and poultry were reported from most areas of China, including provinces bordering other countries, indicating extensive, ongoing geographic spread. The risk to the general public is very low and most human infections were, and continue to be, associated with poultry exposure, especially at live bird markets in mainland China. Throughout the first four epidemics of Asian H7N9 infections, only low pathogenic avian influenza (LPAI) viruses were detected among human, poultry, and environmental specimens and samples. During the fifth epidemic, mutations were detected among some Asian H7N9 viruses, identifying the emergence of high pathogenic avian influenza (HPAI) viruses as well as viruses with reduced susceptibility to influenza antiviral medications recommended for treatment. Furthermore, the fifth-epidemic viruses diverged genetically into two separate lineages (Pearl River Delta lineage and Yangtze River Delta lineage), with Yangtze River Delta lineage viruses emerging as antigenically different compared with those from earlier epidemics. Because of its pandemic potential, candidate vaccine viruses (CVV) were produced in 2013 that have been used to make vaccines against Asian H7N9 viruses circulating at that time. CDC is working with partners to enhance surveillance for Asian H7N9 viruses in humans and poultry, to improve laboratory capability to detect and characterize H7N9 viruses, and to develop, test and distribute new CVV that could be used for vaccine production if a vaccine is needed.

Increasing seasonal influenza vaccination among high risk groups in China: Do community healthcare workers have a role to play?

BACKGROUND: Seasonal influenza vaccine uptake in China is low. This study aims to assess the role of community healthcare workers (HCWs) in increasing vaccination among high risk groups in China. METHODS: We analyzed data from four knowledge, attitude and practice (KAP) studies on seasonal influenza vaccination in China targeting guardians of young children, pregnant women, adults aged ≥60years, and HCWs from 2012 to 2014. RESULTS: Thirty-one percent of pregnant women and 78% adults aged ≥60years reported willingness to follow HCWs' recommendations for influenza vaccination. Guardians were more likely to vaccinate their children if they received HCWs' recommendations (35% vs. 17%, p<0.001). Community HCWs were more likely to recommend seasonal influenza vaccination than hospital HCWs (58% vs. 28%, p<0.001). CONCLUSION: Study results suggest the value of incorporating community HCWs' recommendation for seasonal influenza vaccination into existing primary public health programs to increase vaccination coverage among high risk groups in China.

Preliminary Epidemiology of Human Infections with Highly Pathogenic Avian Influenza A(H7N9) Virus, China, 2017.

We compared the characteristics of cases of highly pathogenic avian influenza (HPAI) and low pathogenic avian influenza (LPAI) A(H7N9) virus infections in China. HPAI A(H7N9) case-patients were more likely to have had exposure to sick and dead poultry in rural areas and were hospitalized earlier than were LPAI A(H7N9) case-patients.