CHICAGO — The total number of intussusception
reports to the Vaccine Adverse Events Reporting System after immunization with
a rotavirus vaccine did not exceed the number expected to occur by chance
alone. However, a new CDC study reports that the possibility of a small
increase in intussusception in the 1-7 day period after dose 1 cannot be
excluded.
The study of Merck’s rotavirus vaccine (RotaTeq)
and data from Vaccine Adverse Events Reporting System (VAERS) by Penina
Haber, MPH, and colleagues from the CDC was presented here during the 51st
Interscience Conference on Antimicrobial Agents and Chemotherapy.
“We were able to verify 518 reports, about 9% of
all reports to VAERS. Of those, 272 reports (about 44%) occurred within 1-21
days of vaccine receipt and 176 (about 58%) of the 272 cases were within 1 to 7
days after vaccinations,” Haber, an epidemiologist with the CDC, said
during her presentation. “Large active surveillance studies would be
needed to further evaluate these findings, but the benefits of the RotaTeq
vaccine in the US would outweigh the small risk of intussusception if
confirmed.”
In February 2006, RotaTeq was approved for use in US
infants. According to the first-year review of adverse events reported to
VAERS, no increased risk of intussusception following RotaTeq was detected.
However, a potential clustering of intussusception cases reported within 1 to 7
days of dose 1 required continued monitoring, according to Haber.
VAERS reports of intussusception following vaccination
with RotaTeq were reviewed. To calculate the rate ratios (RR) of observed vs.
expected number of intussusception cases after vaccination, data on RotaTeq
doses distributed and age-adjusted background rates of intussusception from the
Vaccine Safety Datalink Project were used. This number was calculated assuming
that 75% of distributed doses were administered and 75% of intussusception
cases were reported to VAERS.
During the study period of March 1, 2006, to Sept. 31,
2010, VAERS received 5,511 reports of adverse events following RotaTeq
vaccination; this included 487 confirmed reports of intussusception.
The study results revealed that after any RotaTeq dose
in the three-dose series, a total of 161 intussusception cases within 1 to 7
days of vaccination were reported, compared with 160 cases expected on days 1
to 7 (RR=0.94; 95% CI, 0.74-1.20). A total of 286 intussusception cases were
reported within 1 to 21 days vs. 486 expected in that time period (RR=0.56; 95%
CI, 0.45-0.69).
For the first RotaTeq dose, 66 cases within 1 to 7 days
of vaccination were reported vs. 40 expected (RR=1.47; 95% CI, 0.96-2.26) and
94 intussusception cases within 1 to 21 days were reported vs. 122 expected
(RR=0.65; 95% CI, 0.44-0.94).
For more information:
- #G1-533. Post-licensure Safety Monitoring of RotaTeq Vaccine in the
United States, Vaccine Adverse Event Reporting System, 2006-2010. Presented at:
51st ICAAC. Sept. 17-20, 2011. Chicago.
Disclosure: There were no financial disclosures
reported with this study.