Impact of birth weight at term on rates of hospital admissions following vaccination at 2 months of age

The researchers analyzed data on children born between April 1st 2002 and March 31st 2009 in the province of Ontario. Using the self-controlled case series design, they examined the risk of the combined endpoint of emergency room visit and hospital admission in the immediate three days post vaccination at 2 months of age compared to a control period 9–18 days after vaccination. In term children, they conducted 4 comparisons of relative incidence (RI) of events: (1) 4 lower birth weight quintiles compared to the largest quintile (2) SGA10 infants compared to non SGA10 infants, (3) low birth weight infants (<2500 g) compared to non low birth weight infants and (4) SGA10 infants vaccinated before 60 days compared to those vaccinated after 60 days.