Although mumps vaccine virus has been shown to infect the placenta and foetus, there is no evidence that it causes congenital malformations in humans; (3) In a 15-year survey involving over 1100 pregnant women who received rubella vaccine within 3 months before or after conception (of whom 635 received the Wistar RA 27/ 3 strain), none of the newborns had abnormalities compatible with congenital rubella syndrome; and (4) Wild-type varicella is known to cause foetal harm, and is associated with an increased risk of herpes zoster in the first year of life and severe varicella in the newborn infant.