By a journey to Greece on less than 1 month 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.

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.

Recommended vaccinations Starting Diphtheria 1 day Tetanus 1 day Typhoid 1 week 1 week When to start vaccinations before leaving::