This is a prospective randomized, open label clinical trial in approximately 300 children aged 5-11 years with a physician diagnosis of persistent asthma. Participants will be randomized 1:1 to receive either a single intranasal dose of licensed quadrivalent LAIV (LAIV4) or an intramuscular injection of quadrivalent IIV4 (IIV4).

The study will be conducted at three sites: Vanderbilt University Medical Center (Lead site), Cincinnati Children's Hospital Medical Center (contributing site), and Duke University Medical Center (contributing site) during the 2018-2019 influenza season. Participants will be randomized 1:1 to receive either a single intranasal dose of licensed quadrivalent LAIV (LAIV4) or an intramuscular injection of quadrivalent IIV4 (IIV4), stratifying by asthma severity (mild vs. moderate-to-severe). Vanderbilt will enroll about 100 participants, Cincinnati will enroll about 110 participants, and Duke will enroll about 90 participants. After enrollment, participants will be followed for 43 days via 5 additional phone, email, or text visits to monitor systemic reactogenicity, asthma symptoms and exacerbations, and serious adverse events. The primary objective is to compare proportions of participants with asthma exacerbations during the 42 days after LAIV4 versus IIV4. Because of the potential for increased risk of wheezing after LAIV, the use of LAIV in persons with asthma has been an area of vaccine safety research for many years; the safety issue remains unresolved. A clinical study to assess the safety of LAIV4 in children with asthma could expand the evidence base and inform clinical decision-making and public health policy.

Inclusion Criteria:

• Children between 5-11 years of age, inclusive, at enrollment
• Participant must have a current diagnosis of persistent asthma (Physician diagnosis of asthma and current prescribed use of a long-acting controller medication. For purposes of this study, we have considered "controller" medications to be any single or combination use of long-acting medications used to prevent asthma exacerbations and to achieve long-term control of asthma (as compared to short-acting rescue medication).)
• Parent(s) or legal guardian(s) must provide written, informed consent and participant must provide assent as appropriate for age prior to initiation of study procedures and according to local IRB requirements
• Parent(s) or legal guardian(s) and participant must be willing and able to comply with planned study procedures and be available for all study visits
• Is in good health, other than their asthma, as determined by medical history
• English or Spanish literate (only English-speaking participants will be included at the Cincinnati and Duke sites)
• Intention of being available for entire study period and complete all relevant study procedures, including follow-up using at least one of the following methods: phone calls, text messages, or emails

Exclusion Criteria:

• Acute illness and/or a reported oral temperature of ≥ 100.4°F within 72 hours prior to enrollment (this may result in a temporary delay of vaccination)
• Use of antipyretic medication during the preceding 24 hours that might mask a fever (this may result in a temporary delay of vaccination)
• History of a severe allergic reaction (e.g., anaphylaxis) after a previous dose of any influenza vaccine or after any component of the influenza vaccine, including egg protein.
• Receipt of any licensed vaccine within 14 days (for inactivated vaccines) or 28 days (for live vaccines) prior to vaccination or planned receipt of any licensed vaccine within 42 days after vaccination
• Receipt of current year's (2018-2019 influenza season) licensed influenza vaccine for children 9-11 years (only). (Clarification: Children aged 5-8 years are permitted to be enrolled if they have received zero or one dose of the 2018-2019 influenza season vaccine, and require two doses of the 2018-2019 influenza vaccine.)
• Received an investigational agent (licensed or unlicensed vaccine, drug, biologic, device, blood product, or medication) in the 28 days prior to enrollment or planned receipt before 42 days after vaccination
• Have immunosuppression as a result of an underlying illness or treatment, or use of anticancer chemotherapy or radiation therapy within the preceding 36 months
• Have taken ≥20mg/day of prednisone or its equivalent, for 14 days or more within the past 28 days
• Have known active neoplasm or a history of any hematologic malignancy
• Has had a previous exacerbation of their asthma symptoms requiring systemic steroids within the prior 28 days, or has had a life-threatening exacerbation of asthma in the past two years (e.g. hypoxic seizure, mechanical ventilation)
• Received influenza antiviral medication within 48 hours prior to study vaccination
• History of Guillian-Barré syndrome within 6 weeks of previous influenza vaccination
• Have any condition that, in the opinion of the investigator, would interfere with the evaluation of the responses or would place the participant at unacceptable risk of injury
• Has a positive urine or serum pregnancy test within 24 hours prior to vaccination in a post-menarchal female. LAIV is not recommended for use in pregnant females.
• Currently taking aspirin or aspirin-containing products
• Any parent(s) or legal guardian(s) who is an immediate relative of study staff or is an employee supervised by study staff.

Within 42 days (until day 43) after vaccination.

Adverse events (AEs), including serious adverse events (SAEs) were recorded on the memory aid and included the need for new prescription or nonprescription medications for the control of asthma, an unscheduled healthcare provider visit or consultation, any other clinically significant event at any point during the study period. The definition of SAEs matched the definition from clinicaltrials.gov.