Background: Following the withdrawal of the RotaShield vaccine due to postlicensure surveillance identifying a link to intussusception in approximately 1 out of every 10,000 vaccinated infants, a new monovalent rotavirus vaccine (RV1) was introduced. This prompted an important investigation into the safety profile of RV1 in real-world settings, specifically focusing on the populations of Mexico and Brazil. This study aimed to determine if RV1 vaccination was also associated with an increased risk of intussusception in infants receiving routine immunization in Mexico and Brazil.
Methods: To evaluate the potential association between the RV1 vaccine and intussusception, researchers employed both case-series and case-control methodologies. Active surveillance was conducted across 69 hospitals, encompassing 16 in Mexico and 53 in Brazil, to identify infants diagnosed with intussusception. For each case patient, age-matched control infants from the same neighborhoods were recruited. Vaccination histories were meticulously verified through vaccination cards and clinic records to ascertain RV1 exposure.
Results: The study enrolled a substantial cohort of 615 case patients, with 285 from Mexico and 330 from Brazil, alongside 2050 control infants. The data revealed a significant increase in the risk of intussusception within 1 to 7 days after the first dose of RV1 among infants in Mexico. This elevated risk was consistently observed using both the case-series method (incidence ratio, 5.3; 95% CI, 3.0 to 9.3) and the case-control method (odds ratio, 5.8; 95% CI, 2.6 to 13.0). In contrast, no statistically significant increase in intussusception risk was detected after the first dose in Brazilian infants. However, an increased risk, albeit less pronounced than in Mexico, was observed 1 to 7 days following the second RV1 dose in Brazil, with risk increasing by a factor of 1.9 to 2.6. The study estimated that RV1 vaccination might be associated with an annual excess of 96 intussusception cases in Mexico (approximately 1 per 51,000 infants) and Brazil (approximately 1 per 68,000 infants), potentially contributing to 5 deaths from intussusception. Crucially, the researchers highlighted that the benefits of RV1 vaccination significantly outweighed these risks. It is estimated that RV1 prevents approximately 80,000 hospitalizations and 1,300 deaths annually in Mexico and Brazil due to diarrheal diseases caused by rotavirus.
Conclusions: The findings indicate that RV1 vaccination is associated with a small, short-term increased risk of intussusception, estimated at approximately 1 in every 51,000 to 68,000 vaccinated infants in Mexico and Brazil. Despite this risk, the study underscores that the substantial reduction in rotavirus-related hospitalizations and deaths achieved through RV1 vaccination far surpasses the number of intussusception cases potentially linked to the vaccine. This highlights the overall positive public health impact of RV1 vaccination programs in Mexico and Brazil.
