Astrovirus infections account for nearly 10% of pediatric acute non-bacterial diarrheal illness. Although typically a self-limited illness, childhood diarrhea due to astrovirus and other infectious etiologies disproportionately affects children of lower and middle-income countries (LMICs) and is associated with other adverse outcomes including undernutrition and growth and cognitive developmental delays. Previous studies have suggested that prior infection with astrovirus confers protective immunity against future infections. However, longitudinal data evaluating the potential for protective immunity are limited, particularly for children living in LMICs. To address this knowledge gap, Olortegui et. al. (10.1542/peds.2017-1326) enrolled healthy infants in eight LIMCs and prospectively followed them until two years of age. Stool samples at both asymptomatic and diarrheal symptom time points were actively surveyed for the presence of astrovirus and other enteric pathogens. The study’s cohort included 2,082 children from which over 30,000 stool samples were analyzed. In this study, children experienced a mean of 2.1 astrovirus infections per 100 child-months with a peak incidence occurring between the ages of 6-11 months. By the conclusion of the study, 35% of enrolled children had experienced at least one astrovirus infection, highlighting the potential burden to children living in LMICs. Furthermore, undernutrition was identified as a risk factor for astrovirus-positive diarrhea across the entire cohort. However this was not found to be statistically significant when authors controlled for each testing site.
So does a prior infection with astrovirus confer immunity from a future infection? Olortequi et. al. report a non-significant risk reduction (HR 0.84 [0.71-1.00] p = 0.052) for future infections with astrovirus in children with a prior confirmed infection. Similarly, no protective immunity against astrovirus diarrhea was observed in children with a confirmed prior infection with astrovirus (HR 1.01 [0.74-1.37] p=0.975). Study authors are quick to acknowledge, however, that the lack of protection may well be due to the fact that 77% of all astrovirus diarrheal infections were the result of co-infection with at least one other known enteric pathogen. Taking into account this limitation, the study’s authors posit that vaccination could potentially protect children from an astrovirus infection, particularly because over 70% of infections occur after six months of age, providing a window for the vaccination of infants. Check out this study and see the potential for yourself!