Surveillance methods to detect the impact of a significant cold chain breach

In January 2015, a significant cold chain breach on a postnatal ward in a tertiary hospital in Sydney, Australia was noted to have been occurring since August 2013. Surveillance, amongst the 1178 mothers and 1178 babies affected, for vaccine-preventable diseases (VPDs) and adverse events following immunisation (AEFIs) using linkage with a notifiable diseases database was subsequently undertaken; no directly related instances of VPDs or AEFIs were detected. We evaluate this novel systematic surveillance method which has not been previously reported to determine whether it is effective in determining the impact of cold chain breaches on an individual and population level. The recommendation for revaccination of the affected mothers and subsequent surveillance was resource-intensive and future studies related to such incidents should focus on detailing the resources used to allow the costs versus benefits of such systematic surveillance to be determined.