Josephine van Dongen

Chapter 1 14 are too young to receive rotavirus immunization according to current licensures. 65 Reducing nosocomial infections is par ticularly impor tant for intensive care unit inpatients to prevent se- vere rotavirus disease course. 67 For instance, in premature infants perinatal acquired rotavirus infection can lead to adverse neurological outcomes and cerebral damage. 67 Beneficial non-specific effects are increasingly attributed to live-attenuated vaccines.The mech- anism is not yet fully explained, but via trained or heterologous immunity vaccines seem to provide protection against non-target diseases. For vaccination with Bacillus Calmette-Guerin, measles, polio andVaccinia such effects have been repor ted. 68 For the, relatively new, live-atten- uated rotavirus vaccines the potency of inducing beneficial non-specific effects has not yet been established.After rotavirus vaccination, all-cause hospital admissions were observed to decrease compared to no vaccination in one study. 69 In this paper, an association with type 1 diabetes was studied and as a secondary outcome all-cause non rotavirus hospitalization was assessed.This hospitalization rate was reduced by 31% in the 60 days after rotavirus vaccination compared to an unvaccinated control group, however misclassification of untested acute gastroenteritis hospitalizations might have biased the outcome. Adverse events The globally available vaccines are generally well tolerated and have mild reactogenicity. Ab- dominal cramps and looser stools are the most common adverse events, occurring in one in 10 vaccinated infants.These estimates are based primarily on research in healthy infants. For med- ical risk infants, studies with small populations describe similar adverse event rates. 50,51,56,70,71 For this reason, the general consensus is that the benefits of preventing rotavirus disease outweigh the vaccine side effects for all infants. Rotavirus vaccination has a severe, but rare known adverse event; intussusception. Intussuscep- tion is defined as acute invagination of intestines into each other with acute occlusion as result. Clinical signs and symptoms include bloody stools, severe abdominal pain and/or cramps and, in later stages, abdominal shock. Prolonged intussusception can lead to intestinal necrosis and requires surgical resection of the affected bowel segment. If intussusception is recognized timely and treated with hydrostatic reposition, it can resolve without the need of surgical interven- tion.The cause and pathophysiology of intussusception are not fully understood, neither is the mechanism of vaccine induced intussusception. The incidence of spontaneous intussusception increases with age from three months onwards and peaks around six to eight months. 72 A previous vaccine, RotaShield, was introduced in the United States and withdrawn within one year in 1999, after the association with intussusception, in one in 10.000 vaccinated infants, was demonstrated.This association was not detected in phase III clinical trials. 73 The current available vaccines were therefore extensively investigated with regard to this severe adverse event. 72 Based on the large-scale studies, intussusception is estimated to occur in 1.1 to 2.7 per 100.000 rotavirus vaccinated infants, primarily in the first seven days following the first dose. 74