Recently I was asked to administer yellow fever vaccine to a traveller going to Kenya. Kenya is considered high risk for yellow fever immunisation against yellow fever is a requirement for entering the country.
What many people don’t know when travelling is that adult vaccination is very important to prevent certain diseases. Every country has their own routine vaccine schedule ie from birth to the age of 5 years and then when in primary school for booster doses and some vaccine require booster when entering high school. And this will vary from country to country. However, in adulthood, booster doses are required as well since your immunity to a disease declines over time.
As such, when travelling to another country, especially when the country’s immunisation coverage is below standard expected, always consult your travel doctor and know your requirements prior to taking off. You might be denied entry to a country simple because you did not get a vaccine required for entry.