Chunna Ma

Influenza vaccination coverage rates among adults before and after the 2009 influenza pandemic and the reasons for non-vaccination in Beijing, China: a cross-sectional study.

BackgroundTo optimize the vaccination coverage rates in the general population, the status of coverage rates and the reasons for non-vaccination need to be understood. Therefore, the objective of this study was to assess the changes in influenza vaccination coverage rates in the general population before and after the 2009 influenza pandemic (2008/2009, 2009/2010, and 2010/2011 seasons), and to determine the reasons for non-vaccination.MethodsIn January 2011 we conducted a multi-stage sampling, retrospective, cross-sectional survey of individuals in Beijing who were ≥ 18 years of age using self-administered, anonymous questionnaires. The questionnaire consisted of three sections: demographics (gender, age, educational level, and residential district name); history of influenza vaccination in the 2008/2009, 2009/2010, and 2010/2011 seasons; and reasons for non-vaccination in all three seasons. The main outcome was the vaccination coverage rate and vaccination frequency. Differences among the subgroups were tested using a Pearson’s chi-square test. Multivariate logistic regression was used to determine possible determinants of influenza vaccination uptake.ResultsA total of 13002 respondents completed the questionnaires. The vaccination coverage rates were 16.9% in 2008/2009, 21.8% in 2009/2010, and 16.7% in 2010/2011. Compared to 2008/2009 and 2010/2011, the higher rate in 2009/2010 was statistically significant (χ2=138.96, p<0.001), and no significant difference existed between 2008/2009 and 2010/2011 (χ2=1.296, p=0.255). Overall, 9.4% of the respondents received vaccinations in all three seasons, whereas 70% of the respondents did not get a vaccination during the same period. Based on multivariate analysis, older age and higher level of education were independently associated with increased odds of reporting vaccination in 2009/2010 and 2010/2011. Among participants who reported no influenza vaccinations over the previous three seasons, the most commonly reported reason for non-vaccination was ‘I don’t think I am very likely to catch the flu’ (49.3%).ConclusionsWithin the general population of Beijing the vaccination coverage rates were relatively low and did not change significantly after the influenza pandemic. The perception of not expecting to contract influenza was the predominant barrier to influenza vaccination. Further measures are needed to improve influenza vaccination coverage.

Influenza vaccine effectiveness against medically-attended influenza illness during the 2012-2013 season in Beijing, China.

BACKGROUND Influenza vaccine coverage remains low in China, and there is limited information on the preventive value of local vaccination programs. METHODS As part of influenza virological surveillance in Beijing, China during the 2012-2013 influenza season, we assessed the vaccine effectiveness (VE) of one or more doses of trivalent inactivated influenza vaccine (IIV3) in preventing medically-attended influenza-like-illness (ILI) associated with laboratory-confirmed influenza virus infection using a test-negative case-control design. Influenza vaccination was determined based on self-report by adult patients or the parents of child patients. RESULTS Of 1998 patients with ILI, 695 (35%) tested positive for influenza viruses, including 292 (42%) A(H3N2), 398 (57%) A(H1N1)pdm09, and 5 (1%) not (sub)typed influenza viruses. The rate of influenza vaccination among all patients was 4% (71/1998). Among influenza positive patients, 2% (57/1303) were vaccinated compared to 4% (14/695) among influenza negative patients, resulting in VE for one or more doses of vaccine (adjusted for age, sex, week, and days since illness onset) against all circulating influenza viruses of 52% (95% CI=12-74%). A significant adjusted VE for one or more doses of vaccine for all ages against A(H1N1)pdm09 of 59% (95% CI, 8-82%) was observed; however, the VE against A(H3N2) was 43% (95% CI, -30% to 75%). The point estimate of VE was 59% (95% CI, 19-79%) for those aged <60 years, but a negative VE point estimate without statistical significance was observed among those aged ≥60 years. CONCLUSIONS IIV3 conferred moderate protection against medically-attended influenza in Beijing, China during the 2012-2013 season, especially against the A(H1N1)pdm09 strain and among those aged <60 years old.

A Serological Survey of Antibodies to H5, H7 and H9 Avian Influenza Viruses amongst the Duck-Related Workers in Beijing, China

The continued spread of highly pathogenic avian influenza (HPAI) viruses of H5 and H7 subtypes and low pathogenic avian influenza (LPAI) viruses of H5, H7 and H9 subtypes in birds and the subsequent infections in humans pose an ongoing pandemic threat. It has been proposed that poultry workers are at higher risk of exposure to HPAI or LPAI viruses and subsequently infection due to their repeated exposure to chickens or domestic waterfowl. The aim of this study was to examine the seroprevalence of antibodies against H5, H7 and H9 viruses amongst duck-related workers in Beijing, China and the risk factors associated with seropositivity. In March, 2011, 1741 participants were recruited from (1) commercial duck-breeding farms; (2) private duck-breeding farms; and (3) duck-slaughtering farms. Local villagers who bred ducks in their backyards were also recruited. A survey was administered by face-to-face interview, and blood samples were collected from subjects for antibody testing against H5, H7 and H9 viruses. We found that none of the subjects were seropositive for either H5 or H7 viruses, and only 0.7% (12/1741) had antibody against H9. A statistically significant difference in H9 antibody seroprevalence existed between the various categories of workers (P = 0.005), with the highest figures recorded amongst the villagers (1.7%). Independent risk factors associated with seropositivity toinfection with H9 virus included less frequent disinfection of worksite (OR, 5.13 [95% CI, 1.07–24.58]; P = 0.041; ≤ twice monthly versus>twice monthly) and handling ducks with wounds on hands (OR, 4.13 [95% CI, 1.26–13.57]; P = 0.019). Whilst the risk of infection with H5, H7 and H9 viruses appears to be low among duck-related workers in Beijing, China, ongoing monitoring of infection with the H9 virus is still warranted, especially amongst villagers who breed backyard ducks to monitor for any changes.

The impact of temperature and humidity measures on influenza A (H7N9) outbreaks—evidence from China

OBJECTIVES To examine the non-linear effects of meteorological factors on the incidence of influenza A H7N9 and to determine what meteorological measure, and on which day preceding symptom onset, has the most significant effect on H7N9 infection. METHODS We applied a zero truncated Poisson regression model incorporating smoothed spline functions to assess the non-linear effect of temperature (maximum, minimum, and daily difference) and relative humidity on H7N9 human case numbers occurring in China from February 19, 2013 to February 18, 2014, adjusting for the effects of age and gender. RESULTS Both daily minimum and daily maximum temperature contributed significantly to human infection with the influenza A H7N9 virus. Models incorporating the non-linear effect of minimum or maximum temperature on day 13 prior to disease onset were found to have the best predictive ability. For minimum temperature, high risk was found to range from approximately 5 to 9°C and moderate risk from -10 to 0°C; temperatures of >9°C represented a low risk. For maximum temperature, high risk was found to range from approximately 13 to 18°C and moderate risk from 0 to 4°C; temperatures of >18°C represented a low risk. Relative humidity was not significantly associated with the incidence of infection. The incidence of H7N9 was higher for males compared to females (p<0.01) and it peaked at around 60-70 years of age. CONCLUSIONS We provide direct evidence to support the role of climate conditions in the spread of H7N9 and thereby address a critical question fundamental to our understanding of the epidemiology and evolution of H7N9. These findings could be used to inform targeted surveillance and control efforts aimed at reducing the future spread of H7N9.

Surveillance for avian influenza A(H7N9), Beijing, China, 2013.

During surveillance for pneumonia of unknown etiology and sentinel hospital–based surveillance in Beijing, China, we detected avian influenza A(H7N9) virus infection in 4 persons who had pneumonia, influenza-like illness, or asymptomatic infections. Samples from poultry workers, associated poultry environments, and wild birds suggest that this virus might not be present in Beijing.

Cluster of Human Infections with Avian Influenza A (H7N9) Cases: A Temporal and Spatial Analysis

Objectives: This study aims to describe the spatial and temporal characteristics of human infections with H7N9 virus in China using data from February 2013 to March 2014 from the websites of every province’s Population and Family Planning Commission. Methods: A human infection with H7N9 virus dataset was summarized by county to analyze its spatial clustering, and by date of illness onset to analyze its space-time clustering using the ESRI® Geographic Information System (GIS) software ArcMap™ 10.1 and SatScan. Results: Based on active surveillance data, the distribution map of H7N9 cases shows that compared to the rest of China, the areas from near the Yangtze River delta (YRD) to farther south around the Pearl River delta (PRD) had the highest densities of H7N9 cases. The case data shows a strong space-time clustering in the areas on and near the YRD from 26 March to 18 April 2013 and a weak space-time clustering only in the areas on and near the PRD between 3 and 4 February 2014. However, for the rest of the study period, H7N9 cases were spatial-temporally randomly distributed. Conclusions: Our results suggested that the spatial-temporal clustering of H7N9 in China between 2013 and 2014 is fundamentally different.

A cross-sectional study of factors associated with uptake of vaccination against influenza among older residents in the postpandemic season in Beijing, China.

Objective Annually, influenza epidemics are associated with high mortality rates, notably among elderly persons. The aim of the study was to examine the level of influenza vaccine coverage among Chinese residents aged 60 years and older and to examine the demographic, behavioural and lifestyle health factors associated with vaccine receipt. Design Cross-sectional study. Setting Beijing, China. Participants Stratified sampling was used to recruit participants for this study. A total of 2578 people aged 60 years and older consented to participate in this study. Questionnaires from 2481 participants were valid and were included in the final analysis. Outcome measures Influenza vaccination status and factors associated with vaccination. Methods In late 2010, a survey was conducted with residents from three urban and three rural districts in Beijing, China. Multivariate logistic regression was performed to detect the factors associated with influenza vaccination. Results 2481 older people (aged ≥60 years) were included in the final analysis. In 2010, 44% had received the annual influenza vaccine. Lower education level, poor health status of the participant, regular taking exercises and considering that vaccine is the best measure for preventing influenza were associated with influenza vaccination coverage. Conclusions Influenza vaccine coverage in Beijing still remains suboptimal. Further work needs to be undertaken to ascertain whether the methods used to distribute the vaccine are adequate and whether health professionals are appropriately promoting the vaccine.

Influenza Vaccine Effectiveness in Preventing Influenza Illness Among Children During School-Based Outbreaks in the 2014-2015 Season in Beijing, China.

Background: Little is known about vaccine effectiveness (VE) against nonmedically attended A(H3N2) influenza illness during 2014–2015 when the vaccine component appeared to be a poor match with circulating strains. Methods: Forty-three eligible school influenza outbreaks in Beijing, China, from November 1, 2014, to December 31, 2014, were included in this study. The VE of 2014–2015 trivalent inactivated influenza vaccine (IIV3) was assessed in preventing laboratory-confirmed influenza among school-age children through a case-control design, using asymptomatic controls. Influenza vaccination was documented from a vaccination registry. VE was estimated adjusting for age group, sex, rural versus urban area, body mass index, chronic conditions, onset week and schools through a mixed effects logistic regression model. Results: The average coverage rate of 2014–2015 IIV3 among students across the 43 schools was 47.6%. The fully adjusted VE of 2014–2015 IIV3 against laboratory-confirmed influenza was 38% [95% confidence interval (CI): 12%–57%]. Receipt of previous season’s (2013–2014) IIV3 significantly modified VE of the 2014–2015 IIV3; children who received both 2013–2014 and 2014–2015 vaccinations had VE of 29% (95% CI: −8% to 53%), whereas VE for children who received 2014–2015 IIV3 only was 54% (95% CI: 8%–77%). Conclusions: VE for 2014–2015 IIV3 against A(H3N2) illness identified in schools was modest. Children who did not receive the prior season’s vaccine with a homologous A(H3N2) component may have enjoyed greater protection than repeated vaccinees.

Hygiene Behaviors Associated with Influenza-Like Illness among Adults in Beijing, China: A Large, Population-Based Survey.

The objective of this study was to identify possible hygiene behaviors associated with the incidence of ILI among adults in Beijing. In January 2011, we conducted a multi-stage sampling, cross-sectional survey of adults living in Beijing using self-administered anonymous questionnaires. The main outcome variable was self-reported ILI within the past year. Multivariate logistic regression was used to identify factors associated with self-reported ILI. A total of 13003 participants completed the questionnaires. 6068 (46.7%) of all participants reported ILI during the past year. After adjusting for demographic characteristics, the variables significantly associated with a lower likelihood of reporting ILI were regular physical exercise (OR 0.80; 95% CI 0.74–0.87), optimal hand hygiene (OR 0.87; 95% CI 0.80–0.94), face mask use when going to hospitals (OR 0.87; 95% CI 0.80–0.95), and not sharing of towels and handkerchiefs (OR 0.68; 95% CI 0.63–0.73). These results highlight that personal hygiene behaviors were potential preventive factors against the incidence of ILI among adults in Beijing, and future interventions to improve personal hygiene behaviors are needed in Beijing.

Avian influenza A(H7N9) and (H5N1) infections among poultry and swine workers and the general population in Beijing, China, 2013–2015

Although several studies have reported seroprevalences of antibody against avian influenza A(H7N9) virus among poultry workers in southern China, results have varied and data in northern China are scarce. To understand risks of H7N9 and H5N1 virus infections in northern China, a serological cohort study was conducted. Poultry workers, swine workers and the general population in Beijing, China, were evaluated through three surveys in November 2013, April 2014 and April 2015. The highest seroprevalence to H7N9 virus among poultry workers was recorded in the April 2014 and April 2015 surveys (0.4%), while that to H5N1 clade 2.3.4 or clade 2.3.2.1 virus was noted in the April 2014 survey (1.6% and 0.2%, respectively). The incidence of H7N9 virus infections among poultry workers (1.6/1000 person-months) was significantly lower than that of H5N1 clade 2.3.4 infections (3.8/1000 person-months) but higher than that of H5N1 clade 2.3.2.1 infections (0.3/1000 person-months). Compared with the general population, poultry workers were at higher risk of contracting H7N9 virus (IRR: 34.90; p < 0.001) or H5N1 clade 2.3.4 virus (IRR: 10.58; p < 0.001). Although risks of H7N9 and H5N1 virus infections remain low in Beijing, continued preventive measures are warranted for poultry workers.