Under the "Travel requirements for cruises to the Bahamas and Caribbean" section of the MSC website, it notes that "the vaccination certificate must be valid for the duration of the entire cruise". Is this meant to imply that vaccination certifications expire at some point? My wife and I have been vaccinated for 13 months, but I hadn't heard that there was a need to renew this at any point. Our vaccine cards list the date we were vaccinate, but not a "expiration date".