• We studied susceptibility and vaccination rates in 385 young military recruits. • We found immunity gaps for measles, rubella, varicella, hepatitis A and hepatitis B. • Complete vaccination rates against varicella and hepatitis A were low. • Strategies to access young adults and increase vaccinations should be explored. • A third dose of MMR vaccine should be considered for adolescents in Greece. Data about susceptibility rates in young adults are scarce. We estimated the complete vaccination rates, timeliness of vaccinations and susceptibility rates among male military recruits in Greece. A standardized form was used to collect data. Immunity against measles, rubella, varicella, hepatitis A and hepatitis B was serologically estimated. We studied 385 recruits with a mean age of 23.5 years (range: 18.3–29.9 years). Complete vaccination rates were 94.3% for measles, 100% for rubella, 15% for varicella, 73.9% for hepatitis A and 96.5% for hepatitis B. Only 10.8% of participants were fully vaccinated against all five diseases. Timely vaccination was 47.2% for measles, 89.3% for rubella and 48.1% for hepatitis B. Recruits >23 years had a 1.5-fold increased probability for incomplete vaccinations compared to younger recruits. Laboratory-confirmed immunity rates were 80% against measles, 85.7% against rubella, 85.2% against varicella, 69.4% against hepatitis A and 77.1% against hepatitis B. It is estimated that approximately 388,696 persons aged 18–30 years are susceptible to measles, 277,640 persons to rubella, 287,736 persons to varicella, 595,664 persons to hepatitis A and 444,224 persons to hepatitis B in Greece. Our study showed that young adults have significant immunity gaps against measles, rubella, varicella, hepatitis A and hepatitis B. Complete vaccination rates were suboptimal against hepatitis A and varicella. Strategies to access young adults and increase immunity rates through catch-up vaccination services should be investigated. A third dose of MMR vaccine should be considered for young adolescents in Greece. [ABSTRACT FROM AUTHOR]