We aimed to test the associations between housing, indoor air pollution and children's respiratory health and recurrent fast breathing pneumonia in a poor urban setting in Pakistan. SETTING: Primary health centres in a periurban slum in Karachi, Pakistan. METHODS: Nested matched case control study within a non inferiority randomised controlled trial of fast breathing pneumonia Randomised Trial of Amoxicillin vs Placebo for Pneumonia RETAPP in periurban slums of Karachi, Pakistan. ...