Conclusion may be flawed by inadequate data

EDITOR—Hotopf et al's conclusion that there is an association between ill health in veterans of the Gulf war and immunisations given during the deployment may be flawed by inadequate data.1 2

Before deployment, routine vaccinations are brought up to date and vaccinations specific to deployment are given. For the Gulf conflict a vaccination programme against biological warfare agents had to be implemented—hence the differences between immunisations given before and during deployment. The authors state that personnel received vaccines both before and during deployment, but the results indicate that only 38% of their sample did. We find this proportion to be surprisingly low. The implication that around a third of the force received no vaccinations during the deployment or that a similar proportion had none before deployment is at odds with our review of the immunisation programme.3

The finding that only some 30% of personnel received cholera vaccine before deployment is unexpected. The policy was for all to receive the vaccine before deployment, …