Effectiveness of pandemic H1N1-2009 vaccination in reducing laboratory confirmed influenza infections among military recruits in tropical Singapore.

BACKGROUND: Limited information is available about pandemic H1N1-2009 influenza vaccine effectiveness in tropical communities. We studied the effectiveness of a pandemic H1N1 vaccination program in reducing influenza cases in Singapore. METHODS: A surveillance study was conducted among military personnel presenting with febrile respiratory illness from mid-2009 to mid-2010. Consenting individuals underwent nasal washes, which were tested with RT-PCR and subtyped. A vaccination program (inactivated monovalent Panvax H1N1-2009 vaccine) was carried out among recruits. A Bayesian hierarchical model was used to quantify relative risks in the pre- and post-vaccination periods. An autoregressive generalised linear model (GLM) was developed to minimise confounding. RESULTS: Of 2858 participants, 437 (15.3%), 60 (2.1%), and 273 (9.6%) had pandemic H1N1, H3N2, and influenza B. The ratio of relative risks for pandemic H1N1 infection before and after vaccination for the recruit camp relative to other camps was 0.14 (0.016,0.49); for H3N2, 0.44 (0.035,1.8); and for influenza B, 18 (0.77,89). Using the GLM for the recruit camp, post-vaccination weekly cases decreased by 54% (37%,67%, p<0.001) from that expected without vaccination; influenza B increased by 66 times (9-479 times, p<0.001); with no statistical difference for H3N2 (p = 0.54). CONCLUSIONS: Pandemic vaccination reduced H1N1-2009 disease burden among military recruits. Routine seasonal influenza vaccination should be considered.

Effectiveness of public health measures in mitigating pandemic influenza spread: a prospective sero-epidemiological cohort study.

BACKGROUND: Few studies have validated the effectiveness of public health interventions in reducing influenza spread in real­life settings. We aim to validate these measures used during the 2009 pandemic. METHODS: From 22 June to 9 October 2009, we performed a prospective observational cohort study using paired serum samples and symptom review among 3 groups of Singapore military personnel. "Normal" units were subjected to prevailing pandemic response policies. "Essential" units and health care workers had additional public health interventions (eg, enhanced surveillance with isolation, segregation, personal protective equipment). Samples were tested by hemagglutination inhibition; the principal outcome was seroconversion to 2009 influenza A(H1N1). RESULTS: In total, 1015 individuals in 14 units completed the study, with 29% overall seroconversion. Seroconversion among essential units (17%) and health care workers (11%) was significantly lower than that in normal units (44%) (P = .001). Symptomatic illness attributable to influenza was also lower in essential units (5%) and health care workers (2%) than in normal units (12%) (P = .06). Adjusted for confounders, unit type was the only significant variable influencing overall seroconversion ( P < .05). From multivariate analysis within each unit, age (P < .001) and baseline antibody titer (P = .012 ) were inversely related to seroconversion risk. CONCLUSIONS: Public health measures are effective in limiting influenza transmission in closed environments.

Oseltamivir ring prophylaxis for containment of 2009 H1N1 influenza outbreaks.

BACKGROUND: From June 22 through June 25, 2009, four outbreaks of infection with the pandemic influenza A (H1N1) virus occurred in Singapore military camps. We report the efficacy of ring chemoprophylaxis (geographically targeted containment by means of prophylaxis) with oseltamivir to control outbreaks of 2009 H1N1 influenza in semiclosed environments. METHODS: All personnel with suspected infection were tested and clinically isolated if infection was confirmed. In addition, we administered postexposure ring chemoprophylaxis with oseltamivir and segregated the affected military units to contain the spread of the virus. All personnel were screened three times weekly both for virologic infection, by means of nasopharyngeal swabs and reverse-transcriptase-polymerase-chain-reaction assay with sequencing, and for clinical symptoms, by means of questionnaires. RESULTS: A total of 1175 personnel were at risk across the four sites, with 1100 receiving oseltamivir prophylaxis. A total of 75 personnel (6.4%) were infected before the intervention, and 7 (0.6%) after the intervention. There was a significant reduction in the overall reproductive number (the number of new cases attributable to the index case), from 1.91 (95% credible interval, 1.50 to 2.36) before the intervention to 0.11 (95% credible interval, 0.05 to 0.20) after the intervention. Three of the four outbreaks showed a significant reduction in the rate of infection after the intervention. Molecular analysis revealed that all four outbreaks were derived from the New York lineage of the 2009 H1N1 virus and that cases within each outbreak were due to transmission rather than unrelated episodes of infection. Of the 816 personnel treated with oseltamivir who were surveyed, 63 (7.7%) reported mild, nonrespiratory side effects of the drug, with no severe adverse events. CONCLUSIONS: Oseltamivir ring chemoprophylaxis, together with prompt identification and isolation of infected personnel, was effective in reducing the impact of outbreaks of 2009 H1N1 influenza in semiclosed settings.

Future synergism in diving accident management: The Singapore model.

The popularity of diving as a leisure activity has been an increasing trend in recent years. With the rise of this sport inevitably comes increasing numbers and risk of diving-related injuries and demand for professional medical treatment of such injuries. Concurrently, with hyperbaric oxygen therapy (HBOT) being more readily available, new applications for HBOT have been proven for the treatment of various medical conditions. In Singapore, diving and hyperbaric medicine was largely a military medicine specialty and its practice confined to the Singapore Armed Forces for many years. The new Hyperbaric and Diving Medicine Centre set up in Singapore General Hospital (SGH) offers an excellent opportunity for collaboration between the Singapore Navy Medical Service (NMS) and SGH. This combines the expertise in the field of diving and hyperbaric medicine that NMS provides, with the resources and specialized services available at SGH. This collaboration was officially formalized by the recent signing of a Memorandum of Understanding between the two organisations. The partnership will allow both organisations to leverage on each other's strengths and enhance the development of research and training capabilities. This collaboration will also be an important step towards formal recognition and accreditation of diving and hyperbaric medicine as a medical subspecialty in the foreseeable future, thus helping to develop and promote diving and hyperbaric medicine in Singapore. This synergistic approach in diving accident management will also promote and establish Singapore as a leader in the field of diving and hyperbaric medicine in the region.