Vaccine Safety

Rotavirus Vaccine

Rotavirus is the leading cause of severe diarrhea and dehydration in young infants worldwide. Each year, rotavirus illness is responsible an estimated 453,000 deaths among infants around the world. Before the introduction of a rotavirus vaccine, rotavirus illness caused in an estimated 55,000 to 70,000 hospitalizations and dozens of deaths in the United States each year. To learn more visit Rotavirus and Rotavirus Vaccination.

Currently, there are 2 licensed vaccines that protect infants from rotavirus illness:

Rotarix. The Food and Drug Administration (FDA) licensed this vaccine for use in the U.S. in 2008.
RotaTeq. FDA licensed this vaccine for use in 2006.

Many studies were done before the vaccines were licensed and found that they are safe. Another rotavirus vaccine called RotaShield was licensed in the United States, but was taken off the market in 1999 because of a risk for intussusception (a bowel blockage that is treated in a hospital and may require surgery). To learn more, visit: Withdrawal of RotaShield Vaccine Recommendation.

How CDC Monitors Rotavirus Vaccine

Vaccines continue to be monitored for safety after they are licensed. This is because pre-licensure trials are often too small to detect rare events and special populations may not be adequately represented. Since licensure, CDC and FDA have been closely checking the safety of rotavirus vaccines through 3 monitoring systems. These systems can monitor adverse events (health problems) already known to be caused by vaccines, as well as detect rare adverse events that were not identified during pre-licensure clinical trials. The 3 systems are:

The Vaccine Adverse Event Reporting System (VAERS)–an early warning public health system that helps CDC and FDA detect possible side effects or adverse events following vaccination.
The Vaccine Safety Datalink (VSD) –a collaboration between CDC and 10 health care organizations which monitors and evaluates adverse events following vaccination. Data are available each year from approximately 9.8 million people.
The Clinical Immunization Safety Assessment (CISA) Network– a collaboration between CDC and medical research centers in the U.S. which conduct research on adverse events that might be caused by vaccines.

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A Closer Look at the Safety Data

VAERS

From 2006 through August 2011, VAERS received 518 reports of confirmed intussusception following RotaTeq. Researchers noted a possible cluster of intussusception reports during the first week after the first dose of RotaTeq. This could mean a small increase in risk, but because of the limitations of VAERS, researchers did not draw any firm conclusions from this.
From 2008 through August 2011, VAERS received 37 reports of confirmed intussusception following Rotarix. Because of the small number of reports, researchers were unable to determine if there are any clusters of intussusception following Rotarix.
As of August 2010, the total number of vaccine doses that had been distributed in the U.S. since licensure was approximately 38 million for RotaTeq and approximately 4.7 million for Rotarix.
VAERS has received fewer reports of intussusception following Rotarix than RotaTeq because Rotarix has not been on the market as long and is not as commonly used in the U.S.
VAERS serves as an early warning system for possible adverse events following immunizations, but is not used for formal studies of vaccine risk. CDC encourages healthcare providers and others to report cases of adverse events following vaccination to VAERS.

VSD

The VSD completed the largest study to date, published in the Journal of the American Medical Association (JAMA), to assess the association of RotaTeq and intussusception. The study was conducted from May 2006 to February 2010 to look at intussusception risk among infants 4 to 34-weeks-old at participating VSD study sites. The VSD examined over 800,000 doses of RotaTeq vaccine, including more than 300,000 first doses given. The study looked for an association between the use of RotaTeq and intussusception using two comparison groups—infants who received other vaccines without RotaTeq during the same healthcare visit and the expected number of intussusception healthcare visits based on RotaTeq pre-licensure background rates (from 2001 to 2005). This study found no observed increased risk of intussusception following RotaTeq.
A previous VSD study which included information on about 200,000 doses of RotaTeq during May 2006-May 2008 also found no increased risk of intussusception following RotaTeq. However, VSD cannot rule out a risk as low as that reported in some other studies (see below).
Rotarix has not been used commonly by managed care organizations in the VSD, and therefore VSD has not been able to study the risk of intussusception after Rotarix.

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Further Safety Studies

Before being licensed, RotaTeq and Rotarix were each tested in about 60,000 to 70,000 infants, half of whom got the vaccine and half got a placebo. No increased risk of intussusception was found. Since then, millions of infants in the United States have gotten Rotarix and RotaTeq safely.

After RotaTeq was licensed, an evaluation in the U.S. sponsored by Merck & Co., Inc., its manufacturer, did not show evidence of an increased risk of intussusception. This study also could not rule out a low—level increased risk.
During 2008-2010, CDC collaborated on a study of Rotarix in Mexico and Brazil. In Mexico, there was an increase in the risk of intussusception in the first week after the first dose of Rotarix. However, in Brazil, there was an increased risk in the first week after the second dose of Rotarix.
A safety monitoring study of infants who received Rotarix rotavirus vaccine was conducted in Mexico by the vaccine’s manufacturer, GlaxoSmithKline.
- Final results from this study showed an increased risk of intussusception in infants within 31 days, but particularly after 7 days of getting the first dose of Rotarix.
- Based on this study, it is estimated that approximately 1 to 3 out of 100,000 U.S. infants might develop intussusception within 7 days after receiving the first dose of Rotarix. So far, a risk of intussusception from Rotarix has not been documented in the U.S. However, the current data available do not allow us to exclude a possible low risk like in Mexico.
- This information is now included in the Postmarketing Experience subsection [PDF - 182 KB] of the Adverse Reactions section of the prescribing information and in the information for the patient. For more information, see Update: Information on Rotarix - Labeling Revision Pertaining to Intussusception.
In Australia, post-marketing surveillance studies found an increase in intussusception cases in the first week after vaccination with both Rotarix and RotaTeq vaccines, although these findings are based on a relatively small number of cases.

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Risk vs. Benefits

Some, but not all, studies suggest that RotaTeq and Rotarix vaccines may possibly cause a small increase in the risk of intussusception. This risk has not been documented in the United States so far. However, if the risk seen in other settings were to exist in the US, it is possible that an estimated 1 to 3 U.S. infants out of 100,000 might develop intussusception within 7 days of getting their first dose of rotavirus vaccine. That means 50 to 60 vaccinated U.S. infants might develop intussusception each year.

The benefits of rotavirus vaccines in preventing hospitalizations and deaths from rotavirus illness far outweigh the small possible risk of intussusception. Rotavirus vaccines prevent more than 65,000 hospitalizations from rotavirus illness. CDC continues to recommend routine rotavirus vaccination of U.S. infants.