Mathematical modelling of the impact of treating latent tuberculosis infection in the elderly in a city with intermediate tuberculosis burden.

Hong Kong is a high-income city with intermediate tuberculosis (TB) burden primarily driven by endogenous reactivations. A high proportion of remote latently infected people, particularly elderly, hinders the effectiveness of current strategies focusing on passive TB detection. In this study, we developed a mathematical model to evaluate the impact of treating latent TB infection (LTBI) in the elderly in addition to current TB control strategies. The model was calibrated using the annual age-stratified TB notifications from 1965-2013 in Hong Kong. Our results showed that at present, approximately 75% of annual new notifications were from reactivations. Given the present treatment completion rate, even if only a low to moderate proportion (approximately 20% to 40%) of elderly people were screened and treated for LTBI, the overall TB incidence could be reduced by almost 50%, to reach the 2025 milestone of the global End TB Strategy. Nevertheless, due to a high risk of hepatotoxicity in elderly population, benefit-risk ratios were mostly below unity; thus, intervention programs should be carefully formulated, including prioritising LTBI treatment for high-risk elderly groups who are closely monitored for possible adverse side effects.

Targeting Adults for Supplementary Immunization Activities of Measles Control in Central China: A Mathematical Modelling Study.

Routine immunizations and supplementary immunization activities (SIAs) have significantly improved measles control over the past two decades in China. Progress towards eliminating measles currently faces multiple challenges as the infection age increases, and adult-targeted SIA strategies are being considered. This study developed an age-stratified susceptible-exposed-infectious-recovered model using a recently published contact matrix to depict measles transmissions between individuals in seven age groups. Hubei, a high measles-incidence province in central China, was the selected setting. The baseline scenario was calibrated by fitting with the 2012-2015 age-stratified incidence data. SIAs targeting multiple age groups were simulated. Adult-targeted (>29 years) two-year SIA cycles produced the greatest annual incidence rate decrease, reducing incidences by half over a long timespan with 90% coverage levels. Incidences could remain below 10/100,000 until 2030 if SIAs were provided to individuals ≥6 years old with at least 50% coverage. These findings will help officials prioritize supplementary vaccination strategies. Public health officials in China should consider adult-to-adult transmissions and provide adult-targeted SIAs. Although officials have reported approximately 90% SIA coverage in the past, SIAs for the adult population should be provided on shorter intervals, particularly for the aging population with decreased immunity.

Interpreting the transmissibility of measles in two different post periods of supplementary immunization activities in Hubei, China.

Although evidence has shown that supplementary immunization activity (SIA) campaigns greatly reduce the incidence of measles, their effects on disease transmissibility have seldom been monitored. A great decrease in the number of cases may be a false signal of early success towards measles elimination to policy makers. By interpreting the transmissibility in two different post-SIA periods in Hubei, China, the current study showed sustained measles transmissions despite a reduced number of cases. Two population-based cross-sectional serological surveys of measles antibodies were conducted in Hubei province in mid-2010 and mid-2011 after the implementation of SIAs. Immunoglobulin G (IgG) antibodies against measles were measured by enzyme-linked immunosorbent assay (ELISA). Based on the estimated age-specific susceptibility levels, the effective reproduction number (R), a key indicator of disease transmissibility, was determined by the next generation matrix in transmission model. The results revealed an overall IgG seroprevalence of 88.0% (95% confidence interval [CI]: 85.6-90.4%) and 89.6% (95%CI: 88.0-91.2%), respectively, in the two different periods. Comparatively lower seroprevalence rates were observed among children less than 24months of age and young adults 15 to 19years of age in 2011. The Rs were 0.76 and 1.53 for the two study periods. In conclusion, even though the incidence was reduced to below 1/100,000 in both 2010 and 2011, the reproduction number in 2011 indicates a high risk for sustained measles transmission. This finding was potentially due to a lower seropositivity rate among young adults that had not been covered in the first SIA. Thus, implementation of SIA targeted to appropriate age groups is recommended. Regular monitoring of seroprevalence is also suggested to track disease transmissibility and to align SIA with the appropriate age groups.

Willingness of future A/H7N9 influenza vaccine uptake: A cross-sectional study of Hong Kong community.

We conducted a population telephone survey in Hong Kong during the second wave of influenza A/H7N9 outbreak in 2014. Among the respondents, 50.5% of the respondents would like to accept A/H7N9 vaccination in future. Respondents had poor knowledge of A/H7N9 influenza and vaccines. More than 60% of respondents mixed up seasonal influenza this year and A/H7N9 influenza. Results show that socio-demographic factors were all independent of the vaccine uptake willingness while anxiety level and vaccine history were the main affecting factors. Vaccine promotion strategies may focus on influenza knowledge, attitude and behavior.