不一定

https://www.cdc.gov/yellowfever/vaccine/vaccine-recommendations.html

For most people, a single dose of yellow fever vaccine provides long-lasting protection and a booster dose of the vaccine is not needed. However, travelers going to areas with ongoing outbreaks may consider getting a booster dose of yellow fever vaccine if it has been 10 years or more since they were last vaccinated. Certain countries might also require a booster dose of the vaccine; visit Travelers’ Health for information on specific country requirements.

Talk to your healthcare provider to determine if you need a yellow fever vaccination or a booster shot before your trip to an area at risk for yellow fever.

 反正就是有些risk, 我反正是叉掉南美了