Slight increased risk of intussusception linked to rotavirus vaccination

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1. Pentavalent rotavius vaccine was associated with an excess risk of 1.5 cases of intussusception per 100,000 recipients of the first dose. 

Evidence Rating Level: 2 (Good) 

Study Rundown: Rotavirus is a leading cause of viral gastroenteritis in children worldwide. Prior to the introduction of rotavirus vaccine in the US and Europe, between 1 in 20 and 1 in 80 children under 5 were hospitalized for rotavirus gastroenteritis annually. RotaTeq (RV5), a pentavalent rotavirus vaccine from Merck was licensed in 2006 and Rotarix (RV1), a monovalent vaccine from GlaxoSmithKline, was licensed in 2008. The pentavalent vaccine is more commonly used in the US. It is given to infants orally at 2 months, 4 months and 6 months of age.

Recently, evidence from studies outside the US has suggested an association between the two rotavirus vaccines and intussusception. Intussusception is a condition in which a part of the intestine invaginates, or telescopes, into itself, causing an obstruction. It is a serious condition which can lead to bowel perforation. It is most common in children under the age of 2.

This post-licensure study, conducted by the FDA, investigated this association using data from three large insurers. The study found that the pentavalent vaccine is associated with an excess risk of 1.5 cases of intussusception per 100,000 recipients. There was insufficient data to detect an association between the monovalent vaccine and intussusception. Of note, there were a number of potential cases for which medical charts were missing. The missing charts reduced the power and precision of the study. The observed increase in risk of intussusception should be seen in the context of the significant decrease in hospitalizations and clinic visits for rotavirus gastroenteritis resulting from vaccination.

Click to read the study, published today in NEJM

Click to read an accompanying editorial, published today in NEJM

Relevant Reading: Sustained Decline in Rotavirus Detections in the United States Following the Introduction of Rotavirus Vaccine in 2006; Uptake, Impact, and Effectiveness of Rotavirus Vaccination in the United States

In-Depth [retrospective cohort]: This study analyzed data from children between 5.0 and 36.9 weeks of age in the Aetna, HealthCore, or Humana insurance databases. This includes over 1 million doses of RV5 and about 100,000 doses of RV1. The primary study design was a self-controlled risk-interval, in which the first 21 days after vaccination are the designated “risk interval” and days 22 to 42 after vaccination are the “control interval”. The number of cases of intussusception in the risk interval is compared to the number of cases in the control interval to determine the risk of intussusception from vaccination. This presumes that the first 21 days after vaccination is the relevant at-risk time frame. This is a reasonable assumption under the hypothesis that intussusception after rotavirus vaccination is related to the vaccine causing enlarged lymph nodes in the intestine which can act as lead points for intussusception.

About 150 cases of intussusception were identified in the databases using diagnosis codes and chart review. This number does not include 76 potential cases of intussusception for which the charts were not available. The study found an attributable risk of 1.5 (95% CI 0.2 to 3.2) cases of intussusception per 100,000 first doses of RV5.

By Tomi Jun and Adrienne Cheung

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