Benefits of rotavirus vaccine outweigh potential risks

51st ICAAC

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 to 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 to 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).

Disclosure: There are no financial disclosures reported with this study.

For more information:

Haber P. #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.

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