A Study of JNJ-64281802 for the Prevention of Dengue Infection

Number of participants with DENV infection between baseline and the last day of dosing + 1 day among HHC participants with no evidence of DENV infection at baseline were reported. Presence of a laboratory-confirmed DENV infection was defined as a positive DENV ribonucleic acid (RNA) (assessed using a validated quantitative DENV reverse transcription polymerase chain reaction \[RT-PCR\]) or DENV non-structural protein 1 (NS1); assessed by enzyme-linked immunosorbent assay (ELISA) test result. A sample was considered positive for DENV RNA when the result was 'target detected' (when the result was above the limit of detection of the polymerase chain reaction \[PCR\] assay) or a sample was considered DENV NS1 positive if the qualitative DENV NS1 result was positive (quantitative DENV NS1 result greater than or equal to \[\>=\] 11 relative units per milliliter \[RU/mL\]).

Time frame: Baseline (DB prophylactic Day 1) up to last day of dosing + 1 day (up to DB prophylactic Day 29)

Population: Primary analysis set(PAS): all randomized participants who received at least 1 dose of study intervention, who had no evidence of DENV infection at baseline (based on target not detected \[TND\] results for DENV RNA assay and if available, negative/borderline result for NS1 protein assays) and with at least 1 result for DENV RNA or NS1 protein assay available post baseline up to and including last day of dosing + 1 day. As pre-planned, data collection and analysis was not performed for index case.

Number of participants with abnormalities in physical examination parameters (head/neck/thyroid, eyes/ears/nose/throat, respiratory, cardiovascular, lymph nodes, abdomen, skin, musculoskeletal, and neurological) were reported based on investigator's discretion.

Time frame: Day 50

Population: Safety analysis set included all randomized participants who received at least 1 dose of study intervention. Here, 'N' (overall number of participants analyzed) refers to the number of participants evaluable for this outcome measure. As pre-planned, data collection and analysis was not performed for index case.

Number of participants with laboratory-confirmed symptomatic DENV infection between baseline and last day of dosing + 1 day among all HHC participants (with/without evidence of DENV infection at baseline) were reported. Laboratory confirmed symptomatic DENV infection was defined as having at least 2 solicited systemic adverse events (AEs; retro-orbital pain, fever, arthralgia, headache, myalgia, rash, abdominal pain, nausea, fatigue, loss of appetite, vomiting, and diarrhea) of which at least 1 was a most common dengue symptom (retro-orbital pain, fever, arthralgia, headache, myalgia, rash), lasted for \>=1 day and occurred within +/-2 days time window around positive PCR or NS1 test, between baseline and last day of dosing. Sample was considered positive for DENV RNA when result was 'target detected' (when result was above the limit of detection of PCR assay) or sample considered DENV NS1 positive if qualitative DENV NS1 result was positive (quantitative DENV NS1 result \>=11 RU/mL).

Time frame: Baseline (DB prophylactic Day 1) up to last day of dosing + 1 day (up to DB prophylactic Day 29)

Population: Complete analysis set: All participants included in PAS or secondary analysis set (SAS) (all randomized participants who received at least 1 dose of study intervention, had evidence of DENV infection \[based on positive results for DENV RNA or NS1 protein assays at baseline\] but without DENV signs and symptoms at baseline). As pre-planned, data collection and analysis was not performed for index case.

Number of participants with laboratory-confirmed symptomatic DENV infection between baseline and last day of dosing + 1 day among HHC participants with no evidence of DENV infection at baseline were reported. Laboratory confirmed symptomatic DENV infection was defined as having at least 2 solicited systemic AEs (retro-orbital pain, fever, arthralgia, headache, myalgia, rash, abdominal pain, nausea, fatigue, loss of appetite, vomiting, and diarrhea) of which at least 1 was a most common dengue symptom (retro-orbital pain, fever, arthralgia, headache, myalgia, and rash), lasted for \>=1 day and occurred within a +/-2 days time window around the positive PCR or NS1 test, between baseline and the last day of dosing. A sample was considered positive for DENV RNA when the result was 'target detected' (when result was above the limit of detection of PCR assay) or sample was considered DENV NS1 positive if the qualitative DENV NS1 result was positive (quantitative DENV NS1 result \>=11 RU/mL).

Time frame: Baseline (DB prophylactic Day 1) up to last day of dosing + 1 day (up to DB prophylactic Day 29)

Population: PAS included all randomized participants who received at least 1 dose of study intervention, who had no evidence of DENV infection at baseline (based on TND\] results for DENV RNA assay and, if available, a negative/borderline result for NS1 protein assays) and with at least 1 result for DENV RNA or NS1 protein assay available post baseline up to and including the last day of dosing + 1 day. As pre-planned, data collection and analysis was not performed for index case.

ECG variables: heart rate (HR), PR interval, RR interval, QRS interval, QT interval, and corrected QT (QTc) interval using both following correction methods: QT corrected according to Bazett's formula (QTcB), QT corrected according to Fridericia's formula (QTcF). Abnormalities were categorized as low or high. HR (bpm): low: \< 45, high: \>=120; PR Interval (milliseconds \[ms\]): low: \<110, high: \>=220; QRS interval (ms): high: \>=120; QTcB and QTcF (ms): Borderline prolonged QT: 450\< QTc \<=480, 480 \<QTc \<=500, QTc \>500. Any abnormality occurring at or after initial administration of study intervention until last study-related activity, or participant had been deemed lost to follow-up after demonstration of due diligence of follow up efforts was considered treatment emergent.

Time frame: Day 28

Population: Safety analysis set included all randomized participants who received at least 1 dose of study intervention. Here, 'N' (overall number of participants analyzed) refers to the number of participants evaluable for this outcome measure; 'n' (number analyzed) signifies number of participants analyzed at specified rows. Only those parameters in which at least 1 participant had data was reported in this outcome measure. As pre-planned, data collection and analysis was not performed for index case.

An adverse event (AE) was any untoward medical occurrence in a clinical study participant administered a medicinal (investigational or non-investigational) product. An AE does not necessarily have a causal relationship with the intervention. Serious AE was the AE resulting in any of following outcomes/deemed significant for any other reason: death; initial/prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. TEAEs were defined as any AE occurring at or after initial administration of study intervention until the last study-related activity, or until the participant had been deemed lost to follow-up after demonstration of due diligence of follow up efforts. TEAEs included both serious and non-serious adverse events.

Time frame: DB prophylactic phase: From start of study treatment (Day 1) up to visit Day 50, considering the long half-life (~10 days) of the study intervention; Follow-up phase: From visit Day 50 up to Day 90

Population: Safety analysis set included all randomized participants who received at least 1 dose of study intervention. As pre-planned, data collection and analysis was not performed for index case.

Vital signs: pulse and blood pressure (systolic blood pressure\[SBP\]/diastolic blood pressure\[DBP\]). Abnormality grades determined per Division of Acquired Immunodeficiency Syndrome (DAIDS) for grading severity of adult and pediatric AEs: SBP(millimeters of mercury\[mmHg\]):Hypertension:Grade (G)1(mild):141-150, G2(moderate):greater than (\>)150-155, G3(severe):\>155; SBP(mmHg):Hypotension:G1(mild):85-89, G2(moderate):80 to less than (\<)85, G3(severe):\<80; DPB(mmHg):Hypertension:G1(mild):91-95, G2(moderate):\>95-100, G3(severe):\>100; Pulse(beats per minutes\[bpm\]):Tachycardia: G1(mild):\>100-115, G2(moderate):\>115-130, G3(severe):\>130; Pulse(bpm):Bradycardia:G1(mild):50-54, G2(moderate):\<50-45, G3(severe):\<45. Any abnormality occurring at/after initial administration of study intervention until last study-related activity, or participant had been deemed lost to follow-up after demonstration of due diligence of follow up efforts was considered TE. Worst TE toxicity grade=highest grade reached.

Time frame: From start of drug administration (DB prophylactic Day 1) up to Day 50

Population: Safety analysis set included all randomized participants who received at least 1 dose of study intervention. Here, 'N' (overall number of participants analyzed) refers to the number of participants evaluable for this outcome measure. Only parameter (SBP: Hypertension) in which at least 1 participant had data was reported. As pre-planned, data collection and analysis was not performed for index case.

Number of participants with treatment-emergent worst grade (Grade 3 or 4) abnormalities in laboratory parameters were reported. Laboratory assessments included clinical chemistry, hematology and urinalysis. Abnormality criterions were based on DAIDS: Grade 1= mild, Grade 2= moderate, Grade 3= severe, Grade 4= life-threatening. Any abnormality occurring at or after initial administration of study intervention until the last study-related activity, or until the participant had been deemed lost to follow-up after demonstration of due diligence of follow up efforts was considered treatment emergent.

Time frame: From start of drug administration (DB prophylactic Day 1) up to Day 50

Population: Safety analysis set included all randomized participants who received at least 1 dose of study intervention. Here, 'N' (overall number of participants analyzed) refers to the number of participants evaluable for this outcome measure; 'n' (number analyzed) signifies number of participants analyzed at specified rows. Only those parameters in which at least 1 participant had data was reported in this outcome measure. As pre-planned, data collection and analysis was not performed for index case.

Plasma concentrations of JNJ-64281802 were reported. Plasma samples were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

Time frame: Pre-dose on Day 1; post-dose on Days 3, 5,9, 13, 21, and 28 ; Days 40, 50, and 90

Population: Pharmacokinetic analysis set included all participants who received at least 1 dose of study intervention and who had at least 1 plasma concentration data value after dosing. Here 'N' (overall number of participants analyzed) refers to the number of participants evaluable for this outcome measure, 'n' (number analyzed) refers to all participants evaluable at specified time points. Data for this outcome measure was planned to be collected and analyzed for specified arms only.