Pei-Jun Ting

Publications of Pei-Jun Ting

• Investigation of causes of oseltamivir chemoprophylaxis failures during influenza A (H1N1-2009) outbreaks.

  Authors: Vernon J Lee, Jonathan Yap, Sebastian Maurer-Stroh, Raphael T C Lee, Frank Eisenhaber, Joshua K Tay, Pei Jun Ting, Jin Phang Loh, Christopher W Wong, Boon Huan Tan, Evelyn S C Koay, Paul M Kelly, Martin L Hibberd

  Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology. 02/2011; 50(2):104-8.

  Antiviral post-exposure prophylaxis with oseltamivir has been used as a strategy in mitigating the Influenza A (H1N1-2009) pandemic. There have been few reports of well-documented prophylaxisAntiviral post-exposure prophylaxis with oseltamivir has been used as a strategy in mitigating the Influenza A (H1N1-2009) pandemic. There have been few reports of well-documented prophylaxis failures and the reasons for failure. We report herein a series of 10 cases of prophylaxis failures and explore the reasons behind their prophylaxis failure. In the early pandemic phase, the military employed oseltamivir post-exposure ring-prophylaxis of affected units. From June 22 to July 30, 2009, cases of laboratory-confirmed prophylaxis failures were identified. Nasopharyngeal swabs were collected and tested by PCR. Samples with sufficient RNA material were sent for whole genome sequencing, and screened for mutations that confer oseltamivir resistance, especially the H275Y mutation. Ten cases of laboratory-confirmed prophylaxis failure were identified, with a mean age of 22.3 years. One case was asymptomatic; the remaining 9 had fever or cough but without severe complications. The mean duration of exposure before starting oseltamivir was 1.9 days (SD 0.9), while the mean duration of oseltamivir consumption before symptom onset was 1.9 days (SD 1.4). None of the samples had the H275Y mutation or other known mutations that confer resistance. From the whole genome sequencing, several mutations at the HA (T220S, E275V, T333A, D239G); PB2 (K660R, L607V, V292I); NS1 (F103S), and NP (W104G) gene segments were detected, but none of them were likely to result in anti-viral resistance. Primary prophylaxis failures exhibited mild symptoms without complications; all did not have the H275Y mutation and were unlikely to result from other mutations.

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

  Authors: Vernon J Lee, Chi Hsien Tan, Jonathan Yap, Alex R Cook, Pei-Jun Ting, Jin-Phang Loh, Qiuhan Gao, Mark I Chen, Wee Lee Kang, Boon Huan Tan, Paul A Tambyah

  PloS one. 01/2011; 6(10):e26572.

  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 reducingLimited 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. 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. 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). Pandemic vaccination reduced H1N1-2009 disease burden among military recruits. Routine seasonal influenza vaccination should be considered.

• A clinical diagnostic model for predicting influenza among young adult military personnel with febrile respiratory illness in Singapore.

  Authors: Vernon J Lee, Jonathan Yap, Alex R Cook, Chi Hsien Tan, Jin-Phang Loh, Wee-Hong Koh, Elizabeth A S Lim, Jasper C W Liaw, Janet S W Chew, Iqbal Hossain, Ka Wei Chan, Pei-Jun Ting, Sock-Hoon Ng, Qiuhan Gao, Paul M Kelly, Mark I Chen, Paul A Tambyah, Boon Huan Tan

  PloS one. 01/2011; 6(3):e17468.

  Influenza infections present with wide-ranging clinical features. We aim to compare the differences in presentation between influenza and non-influenza cases among those with febrile respiratoryInfluenza infections present with wide-ranging clinical features. We aim to compare the differences in presentation between influenza and non-influenza cases among those with febrile respiratory illness (FRI) to determine predictors of influenza infection. Personnel with FRI (defined as fever ≥ 37.5 °C, with cough or sore throat) were recruited from the sentinel surveillance system in the Singapore military. Nasal washes were collected, and tested using the Resplex II and additional PCR assays for etiological determination. Interviewer-administered questionnaires collected information on patient demographics and clinical features. Univariate comparison of the various parameters was conducted, with statistically significant parameters entered into a multivariate logistic regression model. The final multivariate model for influenza versus non-influenza cases was used to build a predictive probability clinical diagnostic model. 821 out of 2858 subjects recruited from 11 May 2009 to 25 Jun 2010 had influenza, of which 434 (52.9%) had 2009 influenza A (H1N1), 58 (7.1%) seasonal influenza A (H3N2) and 269 (32.8%) influenza B. Influenza-positive cases were significantly more likely to present with running nose, chills and rigors, ocular symptoms and higher temperature, and less likely with sore throat, photophobia, injected pharynx, and nausea/vomiting. Our clinical diagnostic model had a sensitivity of 65% (95% CI: 58%, 72%), specificity of 69% (95% CI: 62%, 75%), and overall accuracy of 68% (95% CI: 64%, 71%), performing significantly better than conventional influenza-like illness (ILI) criteria. Use of a clinical diagnostic model may help predict influenza better than the conventional ILI definition among young adults with FRI.