A Pharmacoeconomic Study of Post-Exposure Prophylaxis Strategies for Influenza Virus Infections in Japan

Vaccines can prevent influenza (flu) infections and are cost-effective for society and healthcare. However, the cost-effectiveness of post-exposure prophylaxis as a follow-up strategy is unclear. This study aims to evaluate the cost utility of post-exposure prophylaxis and treatment strategies with neuraminidase inhibitors and a cap-dependent endonuclease inhibitor for flu infections from the perspective of healthcare costs in Japan.

A base-case analysis was used to compare oseltamivir, zanamivir, and laninamivir for neuraminidase inhibitors and baloxavir marboxil for the endonuclease inhibitor. The costs of the first visit to a physician and pharmacy were excluded because of the policy on out-of-pocket expenses for post-exposure prophylaxis in Japan. Direct medical costs include the second physician visit, pharmacy and hospital admission expenses, and drug prices, based on the 2020 Japanese Medical Fee Index. The EuroQol-5Dimention-5Level was utilized to measure healthy participants' quality of life scores, with a time horizon of 14 days. Deterministic and probabilistic sensitivity analyses were conducted.

We have found baloxavir marboxil as the post-exposure prophylaxis agent and laninamivir as the treatment agent to be the most cost-effective strategy in Japan, followed by oseltamivir as the post-exposure prophylaxis agent and zanamivir as the treatment agent.

Baloxavir marboxil and oseltamivir are cost-effective prophylactic agents for flu from the perspective of healthcare costs in Japan. This strategy to select baloxavir marboxil or oseltamivir would be helpful to manage a formulary for post-exposure prophylaxis in Japan.