Inclusion Criteria:  Provision of informed consent prior to any study specific procedures. Children should provide assent to join the study, as applicable. The child's parent(s) or legally authorized representative (LAR) must sign the informed consent form (ICF). The LAR must be aged ≥18 years old. Male or female aged between 4 and 8 years inclusive (not having reached his/her 9th birthday by the time of screening. Weigh at least 14 kg or higher. Clinician diagnosed asthma of at least 3 months. Stable on treatment with albuterol PRN and/or ICS and/or leukotriene receptor antagonists (LTRAs) for 2 weeks prior to screening; children taking budesonide in any form at Visit 1 will be switched to another corticosteroid with a washout of budesonide of 3 to 7 days. Demonstrate ability to correctly use the nebulizer and metered-dose inhaler (MDI) device without a spacer. Willingness and ability of the child and parent(s)/LAR to comply with the demands of the study as described in the informed consent/assent.  Exclusion Criteria:  Inability to change from any budesonide therapy to another suitable corticosteroid. History of life-threatening asthma defined as any asthma episode associated with loss of consciousness, intubation or admission to an intensive care unit. Unstable asthma as judged by the Investigator (eg, any change in asthma therapy within 2 weeks prior to screening or use of more than 2 occasions of rescue medication (albuterol) per day within 1 week prior to screening (potential for rescreen). Children receiving regular maintenance treatment with prohibited anti-inflammatory or long-acting bronchodilator asthma medication (inhaled, nebulized, oral, or systemic) within 1 month prior to screening. More than 1 short course of oral/rectal/systemic corticosteroids within 6 months preceding screening (Visit 1), or any oral/rectal/systemic corticosteroids within 30 days prior to screening. Evidence of active concomitant pulmonary disease other than asthma (children with stable allergic rhinitis will be permitted, as long as, there are no changes in the treatment and the medications do not interfere with the analytical assay methods). Upper respiratory infection involving antibiotic treatment not resolved within 14 days prior to Visit 1. Children with a known or suspected hypersensitivity to albuterol/salbutamol, budesonide or any of the excipients used in the IMPs.