Last year, a campaign for NHS Blood and Transplant took letters out of iconic signs and road names across the U.K. in order to highlight the need for blood donations of O, A and B-type blood.

The #MissingType campaign, by Engine, was successful, and also garnered several awards, winning among others a gold Health and Wellness Lion and a bronze Cyber Lion at Cannes. It's now being rolled out internationally, in a new campaign that brings together 25 blood services from around the world, spanning 21 countries. The U.S., Australia, Singapore, Canada, South Africa and Ireland are among those taking part.

The campaign encourages on major companies and brands to leave the letters O, A and B out of their names, and so far those participating by tweeting images of their brand names with the letters missing include Microsoft, Marmite, Aldi, Google and Tesco.

Iconic world landmarks, like the Sydney Opera House and Toronto's city sign, are also taking part. Ordinary people are also being encouraged to drop the letters A, B and O from their names on Twitter, Facebook and Instagram in order to support the cause.

The campaign, which highlights an almost 30% international drop in blood donation worldwide, is a collaboration between various different Engine agencies, including creative agency WCRS, production company Trailer Park and PR arm MHP.