Unmasking the evidence about masks

In the absence of conclusive evidence, the winner is the mask that has the confidence of clinicians

Australian infection control strategies for pandemic influenza are influenced by world authorities — the Centers for Disease Control and Prevention (CDC) and the World Health Organization. WHO guidelines1 take into account the lack of health resources in many communities, and focus on affordability as well as reductions in infection risk. CDC guidelines2 presuppose a well resourced health sector and are aimed at achieving zero risk. The different approaches of the two organisations are manifest in their conflicting recommendations for the type of face mask to use in routine care of patients with influenza: CDC recommends the N95 respirator (equivalent to the P2 mask used in Australia), while WHO recommends the cheaper surgical mask. By giving the world free access to their guidelines, the organisations have saved countries the cost of guideline development. Yet, the gain in risk reduction with the adoption of the CDC’s recommendation is unknown and may not be cost-effective. Conversely, those who opt for the WHO guideline might not appreciate that health care workers (HCWs) in well resourced settings are unlikely to accept a strategy if they perceive it to be significantly riskier than the more costly alternative. The important question is whether either guideline is based on the best evidence and relates the potential risk reduction to the cost involved.