One intussusception case occurred within the first 7 days after the first vaccine dose, and five cases occurred within a week of the second dose. These incidences were no higher than was the background rate of intussusception, so no increased risk of intussusception in the week after either dose was identified, the researchers said.
The relative incidence of intussusception for dose one during days 1-7 was 0.25 (95% confidence interval, less than .001-1.16), and the relative incidence of intussusception for dose two during days 1-7 was 0.76 (95% CI, 0.16-1.87), Dr. Tate and her associates said.
Incidence of intussusception during the period 8-21 days after vaccination included 6 cases after the first dose and 16 cases after the second dose. Intussusception risk in this extended postvaccination period also was no higher than background risk.
“No clustering of cases occurred in any of the risk windows (1-7 days, 8-21 days, or 1-21 days) after receipt of either dose of RV1,” the authors reported.