Effect of increased influenza and pneumococcal vaccine coverage on the burden of influenza among elderly people in Hong Kong versus Brisbane: abridged secondary publication

1. Influenza and pneumococcal vaccine uptake in older adults of Hong Kong has dramatically increased since the SARS outbreak in 2003. This enables estimation of the effect of increased vaccine coverage by comparing the relative change in influenza disease burden with Brisbane, where vaccine coverage remained stable before and after 2003. 2. Compared with the low vaccination period (preSARS), during the first 6 years of high vaccination (post-SARS), influenza-associated excess rates of cardio-respiratory disease, stroke, and ischaemic heart diseases mortality decreased more in Hong Kong than in Brisbane. 3. After the 2009 H1N1 pandemic, excess rates of all-causes mortality increased in Hong Kong but to a lesser extent than in Brisbane. 4. This study provides limited evidence that markedly increased vaccination rates have reduced influenza disease burden in elderly people of Hong Kong.This study was supported by the Health and Medical Research Fund, Food and Health Bureau, Hong Kong SAR Government (#13121282). The full report is available from the Health and Medical Research Fund website (https://rfs1.fhb.gov.hk/index.html)

Is respiratory viral infection really an important trigger of asthma exacerbations in children?

We performed a prospective cohort study from September 2003 to December 2004 to delineate attributing the effect of different respiratory viral infections including newly discovered ones to asthma exacerbations in children in Hong Kong. One hundred and fourteen children aged 6–14 years with chronic stable asthma and on regular inhaled steroid were monitored for respiratory symptoms over a full calendar year from recruitment. They would attend the study clinic if peak expiratory flow rate decreased to below 80% of their baselines, if they met a predefined symptom score, or if parents subjectively felt them developing a cold. Virological diagnosis using virus culture, antigen detection, and polymerase chain reaction methods on nasal swab specimens would be attempted for all these visits irrespective of triggers. Physician diagnosed outcome of each episode was documented. Three hundred and five episodes of respiratory illnesses were captured in the cohort. Nasal specimens were available in 166 episodes, 92 of which were diagnosed as asthma exacerbations, and 74 non-asthma related episodes. Respiratory viruses were detected in 61 of 166 episodes (36.7%). There was no significant difference in virus detection rate between asthma exacerbations (32 out of 97 episodes, 34.8%) and non-asthma respiratory illnesses (29 out of 79 episodes, 39.2%). Although newly discovered respiratory viruses were identified in these episodes, rhinovirus was the commonest organism associated with both asthma exacerbations and non-asthma related episodes. Plausible explanations for much lower virus detection rate than previously reported include improved personal hygiene and precautionary measures taken during respiratory tract infections in the immediate post-severe acute respiratory syndrome period together with a significant contribution of other adverse factors like environmental air pollution. We conclude that not all viral infections in children with asthma lead to an asthma exacerbation and the attributing effect of different triggers of asthma exacerbations in children vary across different time periods and across different localities

Comparison of influenza disease burden in older populations of Hong Kong and Brisbane: the impact of influenza and pneumococcal vaccination

Background: Influenza and pneumococcal vaccine uptake in the older population aged 65 years or over of Hong Kong dramatically increased since the 2003 SARS outbreak. This study is aimed to evaluate the impact of increased coverage of influenza and pneumococcal vaccines by comparing the change of disease burden in the older population of Hong Kong, with the burden in the older population of Brisbane with relatively high vaccine coverage in the past fifteen years. Methods: Time series segmented regression models were applied to weekly numbers of cause-specific mortality or hospitalization of Hong Kong and Brisbane. Annual excess rates of mortality or hospitalization associated with influenza in the older population were estimated for the pre-SARS (reference period), post-SARS and post-pandemic period, respectively. The rate ratios (RRs) between these periods were also calculated to assess the relative change of disease burden. Results: Compared to the pre-SARS period, excess rates of mortality associated with influenza during the post-SARS period in Hong Kong decreased for cardiorespiratory diseases (RR = 0.90, 95% CI 0.80, 1.01), stroke (RR = 0.74, 95% CI 0.50, 1.09), and ischemic heart diseases (RR = 0.45, 95% CI 0.34, 0.58). The corresponding RRs in Brisbane were 0.79 (95% CI 0.54, 1.15), 0.33 (0.13, 0.80), and 1.09 (0.62, 1.90), respectively. Only the mortality of ischemic heart diseases showed a greater reduction in Hong Kong than in Brisbane. During the post-pandemic period, excess rates of all-cause mortality increased in Hong Kong, but to a lesser extent than in Brisbane (RR = 1.41 vs 2.39). Conclusion: A relative decrease (or less of an increase) of influenza disease burden was observed in the older population of Hong Kong after increased coverage of influenza and pneumococcal vaccines in this population, as compared to those of Brisbane where vaccination rates remained stable. The lack of significant findings in some disease categories highlights the challenges of evaluating the benefits of vaccination at the population level.This study was supported by Health and Medical Research Fund (grant number:13121282), from the Research Fund Secretariat, Food and Health Bureau, the Government of the Hong Kong Special Administrative Region