16. (Relevant for the healthy young adults subjects group). Subject is pregnant (or positive urine pregnancy test), or lactating, or of childbearing potential (to be considered of non-childbearing potential, a female must be postmenopausal for at least 1 year, surgically sterile, or using an effective method of contraception or abstinence from at least 4 weeks prior to vaccination and until at least 4 weeks after vaccination).