By a journey to Seychelle Islands on 6 months or longer recommend protection against the following infections:

Diphtheria
Diphtheria is a serious throat infection, which infects from person-to-person through the air. The vaccination should be less than 10 years old otherwise a booster is needed.
Read more about diphteria here.

Tuberkulosis
The vaccine against tuberculosis, BCG, is recommended to people stationed in high-risk areas for more than 6 months, who have not been previously vaccinated. The vaccine contains live bacteria which produces a small wound, as well as scar after healing. The whole process takes 4 to 8 weeks.
Read more about tuberculosis here.

Hepatitis A (infectious hepatitis)
Infectious hepatitis infects through contaminated food and water. Vaccination consists of two injections about 12 months apart, which protects for up to 25 years. The first vaccination protects for 12 months. 
Read more about hepatitis A here.
The hepatitis A vaccine can be combined with the vaccine against hepatitis B

Hepatitis B
Hepatitis B infects through blood, sexual activities and, in small children, through saliva. The vaccination consists of 2 vaccinations about 4 weeks apart and a third 6 months later. The protection is for at least 25 years perhaps life long. 
Read more about hepatitis B here.
The hepatitis B vaccine can be combined with the vaccine against hepatitis A.

HIV in Africa
109 Danes were infected with HIV in Africa between 1991 and 99. Africa is the continent with most HIV infected people. Overall about 8% of the population is infected with infection rates reaching up to 80% in risk groups like prostitutes.
Read more about HIV here.

Tetanus
Tetanus is a complication to wounds contaminated by soil. If there has been a vaccination within the past 10 years it is not necessary to give a booster in case of wounds and accidents. Tetanus vaccinations are usually given in combination with diphtheria vaccine. If you are previously vaccinated, the vaccine can be given right up to departure.

Typhoid
Typhoid is the most serious of the Salmonella infections. There are two types of vaccine: 
1. Vaccine for injection,  one  vaccination protect up to 3 years. 
2. A live vaccine in capsules, which is swallowed. Three capsules are taken 2 days apart and provide protection for a year.
Read more about typhoid here.
Read more about diarrhoea here.

Yellow fever - transit
Certain countries without yellow fever require a valid yellow fever vaccination certificate if you arrives (even in transit) from a country where yellow fever is present. 

If you arrive from a country without yellow fever, there is no requirement for a yellow fever vaccination.

Read more about yellow fever here.

Recommended vaccinations Starting Diphtheria 1 day Tuberkulosis 6 weeks Hepatitis A (infectious hepatitis) 1 week Hepatitis B 3 - 4 weeks HIV in Africa Tetanus 1 day Typhoid 1 week Yellow fever - transit 10 days 6 weeks When to start vaccinations before leaving::