Background Severe infections in adulthood are associated with subsequent short-term cardiovascular disease. Whether hospital admission for sepsis or pneumonia is associated with persistent increased risk (over a year after infection) is less well established. Design The design of this study was as a register-based cohort study. Methods Some 236,739 men born between 1952-1956 were followed from conscription assessments in adolescence to 2010. All-cause cardiovascular disease ( n = 46,754), including coronary heart disease ( n = 10,279) and stroke ( n = 3438), was identified through national registers 1970-2010 (at ages 18-58 years). Results Sepsis or pneumonia in adulthood (resulting in hospital admission) are associated with increased risk of cardiovascular disease in the years following infection. The risk is highest during the first year after the infection, with an adjusted hazard ratio (and 95% confidence intervals) of 6.33 (5.65-7.09) and a notably increased risk persisted with hazard ratios of 2.47 (2.04-3.00) for the second and 2.12 (1.71-2.62) for the third year after infection. The risk attenuated with time, but remained raised for at least five years after infection; 1.87 (1.47-2.38). The results are adjusted for characteristics in childhood, cardiovascular risk factors and medical history in adolescence. Similar statistically significant associations were found for coronary heart disease and stroke. Conclusions Raised risks of cardiovascular disease following hospital admission for sepsis or pneumonia were increased for more than five years after the infection, but with the highest magnitude during the first three years following infection, suggesting a period of vulnerability when health professionals and patients should be aware of the heightened risk for cardiovascular disease.