Tel: +81-3-3416-0181 / Reservation(Hospital): 03-5494-7300
〈Monday~Friday(except national holiday)9A.M.〜5P.M.〉

  • Access
  • Contact Us
  • MENU

The Japan Drug Information Institute in Pregnancy

Information on Influenza Vaccine and Medication


A study investigating the effects of Tamiflu on the fetus during early stages of pregnancy was released by the JDIIP and Toranomon Hospital on June 2015. Of the 86 deliveries by women who took Tamiflu during early stages of pregnancy, one baby was born with a congenital malformation, which was not high compared to the rate of congenital malformations in normal births. It is said that congenital malformations have about a 3% chance of occurring in typical births.
Although we cannot conclude that Tamiflu has no effect on the fetus from this study alone due to the small size of this study, it can be thought that Tamiflu does not have a high risk of causing congenital malformations.


Relenza is a drug that is inhaled and takes effect in specific parts of the body. Because of this, it is known that the amount of Relenza that circulates in the blood is very small, even if the medication is accidentally swallowed.
Therefore, it is considered that taking Relenza does not pose a threat to infants.

Influenza Vaccine

Influenza vaccines in Japan are considered safe to use in all stages pregnancy, as they are not live vaccines. Therefore, no serious side effects are thought to occur during pregnancy. Studies also suggest that there are no risks of birth deformities using conventional influenza vaccines during early stages of pregnancy.

The Ministry of Health, Labor and Welfare are also investigating if new influenza vaccines, Tamiflu and Relenza are safe to use during pregnancy.

Return to top of page