Duration of fever and other symptoms after laninamivir octanoate hydrate
inhalation over eight influenza seasons
Abstract
Background: Laninamivir octanoate hydrate (laninamivir) is a commonly
used drug for influenza virus. This study is part of our long-term,
systematic surveillance to monitor its effectiveness. Methods: We
investigated the duration of fever and other symptoms after laninamivir
inhalation for the outpatients in the Japanese 2017/18 and 2018/19
influenza seasons, then compared the results with those of the previous
six seasons. Results: The number of laboratory confirmed patients
analyzed was 111 in the 2017/18 season and 84 in 2018/19. The median
duration of fever for B was significantly longer than for A in the
2017/18 season (p = 0.0182). In the 2018/19 season, when we could
compare only between A subtypes, the median duration of fever was
significantly longer for A (H3N2) (p = 0.0290). In contrast, the
differences in the median duration of other symptoms were not
significant. With the previous six seasons added, we evaluated the data
of 1,473 patients over eight sequential influenza seasons. Seasonal
differences were observed in the prevailing types/subtypes. The median
duration of fever among the types/subtypes was significantly different
in some seasons, and it was generally longer for B than for A. The
difference in the duration of fever among the eight seasons was all
within 24 hrs, and it was statistically significant only for A (H3N2).
Conclusions: These results indicate the continuing clinical
effectiveness of laninamivir against all types/subtypes of influenza
virus, despite its broad use in Japan. Longer duration of fever for B
than for A was observed after laninamivir inhalation.