Trial Outcomes & Findings for Dose-Finding Trial to Evaluate the Safety and Immunogenicity of Cytomegalovirus (CMV) Vaccine mRNA-1647 in Healthy Adults (NCT NCT04232280)

mRNA-1647-P202 was a 2-part study. For Part 1, participants were randomized to receive 1 of 3 dose levels (50, 100, 150 micrograms \[ug\]) of the mRNA-1647 vaccine and placebo in CMV-seronegative and CMV-seropositive male and female participants. For Part 2, new female participants (that is, did not participate in Part 1) who were either CMV-seronegative or CMV-seropositive were randomized to receive either the mRNA-1647 vaccine (100 ug) or placebo.

Data were collected based on participant serostatus and the treatment group to which the participant was randomized regardless of the part of the study.

Dose-Finding Trial to Evaluate the Safety and Immunogenicity of Cytomegalovirus (CMV) Vaccine mRNA-1647 in Healthy Adults

Solicited ARs were selected signs and symptoms occurring after vaccination administration during a specified post-vaccination follow-up period. The occurrence and intensity of the selected signs and symptoms was actively solicited from the participant during a specified post-vaccination follow-up period (day of vaccination and 6 subsequent days), using a predefined checklist in the electronic diary. The following local ARs were solicited: pain at injection site, erythema (redness) at injection site, swelling/induration (hardness) at injection site, and localized axillary swelling or tenderness ipsilateral to the vaccination arm. The following systemic ARs were solicited: headache, fatigue, myalgia (muscle aches all over the body), arthralgia (aching in several joints), nausea/vomiting, rash, fever, and chills. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

An unsolicited AE was defined as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. The treatment-emergent AEs are defined as any event not present before exposure to study drug or any event already present that worsened in intensity or frequency after exposure. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section."

An MAAE is an AE that lead to a visit to a healthcare practitioner (HCP). This would include visits to study clinic for unscheduled assessments (for example, rash assessment, abnormal laboratory follow-up), and visits to HCPs external to the clinical site (for example, urgent care, primary care physician). A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section."

An SAE was defined as any untoward medical occurrence that, in the view of either the Investigator or the Sponsor, resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization (hospitalization or prolongation of hospitalization in the absence of a precipitating event was not in itself an SAE), resulted in persistent disability/incapacity, was a congenital anomaly/birth defect, or was a medically important event. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section."

Blood samples for antibody-mediated immunogenicity (AMI) analysis were collected during protocol-specified study visits. Serological assessment of serum anti-CMV neutralizing antibody titers against epithelial cell infection and fibroblast infection were measured by a neutralization assay. Results are reported as fold dilution (titer). GMT 95% confidence interval (CI) was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.

Blood samples for antibody-mediated immunogenicity analysis were collected during protocol-specified study visits. Serological assessment of serum anti-CMV neutralizing antibody titers against epithelial cell infection and fibroblast infection were measured by a neutralization assay. The GMR measures the changes in immunogenicity titers within participants. Results are reported as a ratio (post-baseline/baseline titers). GMR 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.

Blood samples for antibody-mediated immunogenicity analysis were collected during protocol-specified study visits. Serological assessment of serum anti-CMV nAb titers against epithelial cell infection and fibroblast infection were measured by a neutralization assay. A ≥z-fold increase from baseline at participant level was defined as a ≥z \* the lower limit of quantification (LLOQ) for participants with baseline antibody level below the LLOQ, or a z-times or higher-level ratio in participants with baseline antibody level equal to or above the LLOQ. LLOQ=16. Results are reported as percentage of participants with ≥2-fold, 3-fold, and 4-fold increases in serum anti-CMV nAb titers from baseline. 95% CI for percentage is calculated using the Clopper-Pearson method.

Blood samples for antibody-mediated immunogenicity were collected during protocol-specified study visits. Serological assessment for anti-gB-specific IgG and anti-pentameric gH/gL/UL128/UL130/UL131A glycoprotein complex (Pentamer)-specific IgG binding was measured with ELISA. The GMT measures the level of inhibition of anti-gB-specific IgG (anti-gB) and anti-Pentamer-specific IgG (anti-Pentamer) against cytomegalovirus. Results are reported as fold dilution (titer). GMT 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.

Blood samples for antibody-mediated immunogenicity were collected during protocol-specified study visits. Serological assessment for anti-gB-specific IgG and anti-Pentamer-specific IgG binding was measured with ELISA. The GMR measures the changes in immunogenicity titers within participants. Results are reported as a ratio (post-baseline/baseline titers). GMR 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation. Number Analyzed = participants who were evaluable at specified timepoints.

Blood samples for antibody-mediated immunogenicity analysis were collected during protocol-specified study visits. Serological assessment of serum anti-CMV nAb titers against epithelial cell infection and fibroblast infection were measured by a neutralization assay. Results are reported as fold dilution (titer). GMT 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.

Blood samples for antibody-mediated immunogenicity analysis were collected during protocol-specified study visits. Serological assessment of serum anti-CMV nAb titers against epithelial cell infection and fibroblast infection were measured by a neutralization assay. The GMR measures the changes in immunogenicity titers within participants. Results are reported as a ratio (post-baseline/baseline titers). GMR 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.

Blood samples for antibody-mediated immunogenicity analysis were collected during protocol-specified study visits. Serological assessment of serum anti-CMV nAb titers against epithelial cell infection and fibroblast infection were measured by a neutralization assay. A ≥z-fold increase from baseline at participant level was defined as a ≥z \* the LLOQ for participants with baseline antibody level below the LLOQ, or a z-times or higher-level ratio in participants with baseline antibody level equal to or above the LLOQ. LLOQ=16. Results are reported as percentage of participants with ≥2-fold, 3-fold, and 4-fold increases in serum anti-CMV nAb titers from baseline. 95% CI for percentage is calculated using the Clopper-Pearson method.

Blood samples for antibody-mediated immunogenicity were collected during protocol-specified study visits. Serological assessment for anti-gB-specific IgG and anti-Pentamer-specific IgG binding was measured with ELISA. Results are reported as fold dilution (titer). GMT 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.

Blood samples for antibody-mediated immunogenicity were collected during protocol-specified study visits. Serological assessment for anti-gB-specific IgG and anti-Pentamer-specific IgG binding was measured with ELISA. The GMR measures the changes in immunogenicity titers within participants. Results are reported as a ratio (post-baseline/baseline titers). GMR 95% CI was calculated based on the t-distribution of the log-transformed values then back transformed to the original scale for presentation.