MSL's Always research found that nearly a tenth of UK girls, a seventh of Canadian girls and a fifth of those in the US have either left school early or missed it entirely because of lack of access to period products.
That can lead to girls falling behind, missing out on other activities and suffering dips in confidence.
MSL decided that the fact this was an issue – even in developed countries – would prove a powerful rallying cry.
The #EndPeriodPoverty campaign, which scooped Global PR Breakthrough and Global Creative Idea gongs at last night's ceremony, was designed to raise awareness of the issue and encourage donation of Always products to girls in need.
The campaign had normous global reach through 266 earned media placements and 816 influencer posts, with a huge spike in mentions of the term 'period poverty', including nearly 30 million pad donations in the US and UK alone.
PRWeek news editor Arvind Hickman cauught up with the MSL team at last night's awards to find out more about what makes this campaign so special.