A systematic review and meta-analysis concludes that while neuraminidase inhibitors can reduce the duration of seasonal flu in healthy adults by half to one day, overall their use in otherwise healthy adults is unlikely to be appropriate.

This review was carried out on behalf of NICE, with the aim of evaluating the effectiveness and cost-effectiveness of prescribing oseltamivir and zanamivir for seasonal influenza in otherwise healthy individuals and those with co-morbidities. It is intended to inform an update of current NICE guidance on the subject (TA58). A previously published reliable systematic review was used to identify relevant controlled trials published before 2001, and a comprehensive literature search used to identify any subsequent published and unpublished studies. Eligible trials compared a neuraminidase inhibitor with placebo, best symptomatic care, or each other. Results were evaluated for healthy adults (i.e., adults without known co-morbidities) and people at-risk of influenza-related complications.

There were 26 relevant trials, 13 each for zanamivir and oseltamivir. For zanamivir, six trials (n=2701) compared the drug with placebo in otherwise healthy adults, and seven trials (n=1,252) in the overall at-risk population; four trials (n=1,410) compared oseltamivir with placebo in otherwise healthy people and six (n=1,472) compared it with placebo in patients with co-morbidities.

Overall, zanamivir reduced the median time to symptom alleviation in healthy adults by 0.57 days (95% CI −1.07 to −0.08; p=0.02), and oseltamivir 0.55 days (95% CI −0.96 to −0.14; p=0.008).

In those at risk, zanamivir reduced the median time to symptom alleviation by 0.98 days (95% CI −1.84 to −0.11; p=0.03), and oseltamivir reduced it by 0.74 days (95% CI −1.51 to 0.02; p=0.06).

The authors discuss the various options available and conclude that “In view of the advantages and disadvantages of different management strategies for controlling seasonal influenza in healthy adults, recommending the use of antiviral drugs for the treatment of people presenting with symptoms is unlikely to be the most appropriate course of action.” For people who are at increased risk of suffering influenza-related complications, “it is reasonable to recommend precautionary treatment”. They suggest that further research is desirable on the cost-effectiveness of extending vaccination policy to all UK working-age adults.