Observational Study to Estimate the Changes in the Efficacy of BCG with Time Since Vaccination

PI: Laura Rodrigues, Punam Mangtani, Ibrahim Abubakar
Funder: NIHR

BCG vaccination until 2005, was given mostly at school children; since then it is given to infants if required. We know that BCG is a relatively good vaccination when given at school-age, but we do not know the exact protection. We do not know if any effect decreases even further with more time since vaccination, and we do not know the effect of vaccination in infancy in the UK, or how much the effect changes with time since vaccination. It is important to know how long BCG protection lasts (and at what level) for the government to be able to decide how best to use BCG (or any new vaccines given in addition to BCG in the future) to continue to prevent ill health. This study will find out how long the effect of BCG lasts (and at what level) both for vaccine given to infants and given to school children. This will be done in two observational studies comparing frequency of past BCG vaccination in people both with and without a history of ill health. We will find out if subjects were vaccinated or not by examining their arms for a vaccine scar. Scar is a good indication of past vaccination in other countries; we will do a validation study to find out if, in this country also, scar is a good indication of having had BCG vaccination. We will do this by investigating presence of scar in study subjects for whom vaccine records are available. Duration of the effect of infant BCG will be calculated by looking at protection in age groups up to and including 17 year olds, and for BCG vaccination in adolescents up to 24 years after vaccination i.e. in age groups up to the age of 37 years. A successful outcome will consist of the production of good estimates of how long the effect of BCG vaccine lasts when it is given to infants and when it is given to school children. We do not anticipate ethical concerns as the study will not involve interventions: all we will ask participants to do is to let us examine their arms for a BCG scar and answer some questions about their vaccination history, background and history of illnesses. Subjects will be approached by trained interviewers, who will explain the study and ask if they are willing to participate.

Two analytic observational studies are approaching conclusion  comparing the frequency of the BCG vaccine in people in people with and without a history of illhealth. Both studies will evaluate how the effect of BCG vaccine changes with time since vaccination. The first study will examine children aged from 0-17 years, born when BCG can be given in infancy. The second study will examine an adult age range from 23 to 37 years and aged 13-years old when the pre-2005 school aged BCG programme existed.