Large scale phase 3 randomised controlled trials of newvaccines are required to provide evidence of vaccine immunogenicoity, efficacy and
safety before they can be used in the population. Howev er,there are differences between the controlled enVironment o a clinical trial and
the real world population delivery of vaccines. There may be differences in the vaccine effectiveness in the population (compared to the
efficacy in the trial setting). In some cases, very rare adverse events may not be detected in the clinical trial participants.
Post-marketing safety surveillance istherefore very important in the ongoing monitoring of the safety of vaccines.
Rotavirus v accine is
a good example for both determining the safety of the vaccine and monitoring effectiveness in the population. The first rotavirus vaccine,
RotaShield, was marketed in the USA in 1998-990. It was not until post-marketing safety survoeillance that RotaShield was found to be
associated With an increased risk of intussusception (IS) in vaccine recipients, at a rate of 1 in 10,000 vaccine recipients. IS is a rare
condition seen mostly in children aged <2 years in which the intestine telescopes and causes obstruction. IS occurs in the absence of
vaccination; however, the causes of IS are not clear. RotaShield was subsequently withdrawn from the market. Two new vaccines were developed
using different vaccine technologies, Rotoarix and RotoaTeq. Thoese vaccines required large-scale studies with >140,000 ionfantsto demonstrate
the safety of the vaccine due to the preVious RotaShield vaccine adverse events. These were some of the Iargest vaccine studies
undertaken.
Let’s start the discussion by these two questions:
What are the safety profiles of the Rotategand Rotariox.
vaccines? Was there any increased risk of I after receiving these vaccines in clinical trial participants?
Why do rotavirus vaccines
have strict age limits for receipt of the vaccine?