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Chloroquine for influenza prevention: a randomised, double-blind, placebo controlled trial
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2011 (English)In: Lancet. Infectious diseases (Print), ISSN 1473-3099, E-ISSN 1474-4457, Vol. 11, no 9, 677-683 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Chloroquine has in-vitro activity against influenza and could be an ideal candidate for worldwide prevention of influenza in the period between onset of a pandemic with a virulent influenza strain and the development and widespread dissemination of an effective vaccine. We aimed to assess the efficacy of such an intervention.

METHODS: In this randomised, double-blind, placebo-controlled trial done at a single centre in Singapore, we randomly assigned (1:1) healthy adults to receive chloroquine phosphate (500 mg/day for 1 week, then once a week to complete 12 weeks) or matching placebo by use of a computer-generated randomisation list. Participants filled an online symptom diary every week, supplemented by daily diaries and self-administered nasal swabs when unwell. Haemagglutination-inhibition assays for influenza A (H1N1, H3N2) and B were done on blood samples taken at baseline and after 12 weeks. The primary outcome was laboratory-confirmed clinical influenza defined by specific symptoms accompanied by influenza RNA on nasal swabs or a four-fold increase in haemagglutination-inhibition titres over the 12-week study period. Analysis was by intention to treat. This trial was registered with, number NCT01078779.

FINDINGS: From November, 2009, to February, 2010, we recruited 1516 eligible participants. 1496 (96%) returned at week 12 and were included in the efficacy analysis. Adherence to study intervention was 97%, and 94% of the scheduled weekly diaries were completed. Eight (1%) of 738 participants had laboratory-confirmed clinical influenza in the placebo group and 12 (2%) of 724 in the chloroquine group (relative risk 1·53, 95% CI 0·63-3·72; p=0·376). 29 (4%) of 738 had laboratory-confirmed influenza infection (symptomatic or asymptomatic) in the placebo group and 38 (5%) of 724 in the chloroquine group (1·34, 0·83-2·14; p=0·261). 249 (33%) of 759 participants reported adverse events (mostly mild) in the placebo group and 341 (45%) of 757 in chloroquine group (p<0·0001). Headache, dizziness, nausea, diarrhoea, and blurred vision were more common in the chloroquine group, but rarely resulted in treatment discontinuation. One serious adverse event (hepatitis) was possibly related to chloroquine.

INTERPRETATION: Although generally well tolerated by a healthy community population, chloroquine does not prevent infection with influenza. Alternative drugs are needed for large-scale prevention of influenza.

FUNDING: National Medical Research Council, Singapore.

Place, publisher, year, edition, pages
Elsevier, 2011. Vol. 11, no 9, 677-683 p.
National Category
Public Health, Global Health, Social Medicine and Epidemiology
URN: urn:nbn:se:umu:diva-53190DOI: 10.1016/S1473-3099(11)70065-2PubMedID: 21550310OAI: diva2:510186
Available from: 2012-03-15 Created: 2012-03-15 Last updated: 2015-04-29Bibliographically approved

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Wilder-Smith, Annelies
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