The Evolution of the Use of Oseltamivir (Tamiflu) in Seasonal and Pandemic Influenza: A Review of Recommendations From Market Approval to Present Day

Oseltamivir phosphate, also known as Tamiflu ® , is a neuraminidase inhibitor antiviral drug that has been a key intervention for the treatment and prevention of influenza since its market approval in 1999. Despite widespread acknowledgement of oseltamivir as a first-line treatment for severe influenza, its prescribing and use have been subject to debate over the years, as evidence has continually emerged challenging the magnitude of its benefits. Recommendations and advice published by the World Health Organisation (WHO) have been updated several times since the organisation first endorsed the drug in 2002, in response to the current global situation and the best available evidence at the time. Oseltamivir gained particular prominence during the H1N1 swine flu pandemic in 2009, with various countries utilising stockpiles and ethical reviews of its distribution. The aftermath of this event prompted huge research activity, including multiple Randomized Controlled Trials (RCTs) and seminal Cochrane Reviews, which led to an evolution in recommendations by guideline developers. In light of recent changes to the WHO treatment guidelines, this comprehensive narrative review aims to examine key events in the history of oseltamivir, marked by changes in guideline recommendations and the publication of seminal papers in the field. To our knowledge, this review paper is the first to present a chronological analysis of research on oseltamivir alongside key events in guideline development, offering a key insight into the background and context of this antiviral therapeutic and prophylactic drug.