Estriol is a natural estrogen, that is available as vaginal cream and ovule in the Netherlands. It is mainly indicated for relief of postmenopausal symptoms in women with estrogen deficiency. In clinical practice, it is often used as prevention of urinary tract infections in postmenopausal women.
In 2008 Lareb described 13 reports of influenza like illness or pyrexia associated with vaginal application of estriol. In this update Lareb describes 49 cases, received until November 2015. In 36 cases, a positive dechallenge was reported, and in 20 women, estriol was reintroduced and they experienced a similar reaction (positive rechallenge). Marketing Authorization Holder Aspen of estriol (Synapause) has decided that influenza-like symptoms will be added to the SmPC/PIL.
More information regarding influenza, like reactions associated with the use of vaginal estriol, can be found here.