Can an adult such as 30 years old get a pcv 13 (prevnar) vaccine? does it last for a lifetime? what are its advantages and disadvantages? thank you.

Yes/unlikely/...: That vaccine can be safely given to anyone not allergic to one of its components (rare).It is usually recommended only to those at more risk of Pneumococcal disease. (infants, immune deficient, older folks). When given any selective immune boost it provides likely fades in 5+ years. If you are in a population at risk it helps protect you. If not, it may not be worth the time/effort/expense.

Depends: PCV 13 (pneumococcal conjugated vaccine 13) is indicated for adults in 19-64 years of age at higher risk to develop serious pneumococcal infection due to immunocompromising condition, CSF leak, or cochlear implant. One dose of PCV 13, follow up with PPSV23, e.g., pneumovax, after 8 weeks.