Airports around the world are being advised to step up security efforts to protect Covid-19 vaccine shipments amid police warnings of potential targeting from criminal networks, Reuters reports.

The recommendation from a global airports body comes as pharmaceutical companies and airlines are carrying out the largest logistical operation of its kind to distribute vaccines designed to combat the global pandemic.

As part of a broader advisory bulletin on vaccine distribution recently sent to members, Airports Council International recommended affected airports liaise with local authorities and conduct risk assessments on shipments given potential threats.

The bulletin was posted Friday on the group’s website, a spokesman said.