Recently, I got vaccinated with yellow fever vaccine as I am planning to travel to Kenya, a high risk country for yellow fever, in the near future. The vaccine takes 10 days to produce the required antibodies, so it should be taken at least 10 days before the date of departure to the at-risk country. In order to get vaccinated, I searched for vaccination centers in Delhi for yellow fever. I found this page by the Indian government which lists vaccination centers for yellow fever all over India. From that list, I made a phone call to the Airport Health Organization, a vaccination center near to the Delhi Airport.
They asked me to write an email stating that I need yellow fever vaccination. After sending the email, they requested a scanned copy of my passport. Subsequently, they emailed me my appointment date, asking me to pay 300 INR in advance along with other instructions.
You have to reach vaccination center at any time between 10 AM to 12 noon. I got there at around 11 AM on my appointment date and got vaccinated in around 40 minutes, followed by obtaining a vaccine certificate in half an hour. One dosage of this vaccine gives immunity against yellow fever for lifetime. Therefore, I can travel to any country at risk of yellow fever. Although some countries may require proof of vaccination within some time frame and some people might need a booster dose to maintain immunity.