Effective vaccines are not yet available for many important infections, including Most sexually transmitted infections (eg, HIV infection, herpes, syphilis, gonorrhea, chlamydial infections) Tick-borne infections (eg, Lyme disease, ehrlichiosis and anaplasmosis, babesiosis) Many tropical diseases (eg, Chikungunya disease) Many emerging diseases (eg, West Nile virus infection, Zika virus infection) Certain vaccines are recommended routinely for all adults at certain ages who have not previously been vaccinated or have no evidence of previous infection.