In 1962, the World Health Organization proposed that countries will issue stamps in order to help fund the "global program for the eradication of Malaria" and increase world-wide publicity and education about the fight against Malaria. 144 postal administrations issued stamps and souvenir sheets, several of them with the slogan: "The world united against Malaria" ("Le monde uni contre le Paludisme").
Here is the set issued by Tunisia on April 7, 1962:
I have no information about the designer and engraver of this stamp:
Designed by Hatem El Mekki
and engraved by André Frères
Designed by Tijani Allouze
and engraved by Jean Miermont