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Clinical Trial
. 2025 Dec;21(1):2436714.
doi: 10.1080/21645515.2024.2436714. Epub 2025 Jan 21.

Safety and immunogenicity of an mRNA-1273 vaccine booster in adolescents

Amparo L Figueroa  1 , Kashif Ali  2 , Gary Berman  3 , Wenqin Xu  4 , Weiping Deng  4 , Bethany Girard  5 , Anne Yeakey  6 , Karen Slobod  7 , Jacqueline Miller  8 , Rituparna Das  8 , Frances Priddy  8 ; on behalf the TeenCOVE Study Group; List of TeenCOVE Investigators
Collaborators, Affiliations
Clinical Trial

Safety and immunogenicity of an mRNA-1273 vaccine booster in adolescents

Amparo L Figueroa et al. Hum Vaccin Immunother. 2025 Dec.

Abstract

Safety, immunogenicity, and effectiveness of an mRNA-1273 50-μg booster were evaluated in adolescents (12-17 years), with and without pre-booster SARS-CoV-2 infection. Participants who had received the 2-dose mRNA-1273 100-µg primary series in the TeenCOVE trial (NCT04649151) were offered the mRNA-1273 50-μg booster. Primary objectives included safety and inference of effectiveness by establishing noninferiority of neutralizing antibody (nAb) responses after the booster compared with the nAb post-primary series of mRNA-1273 among young adults in COVE (NCT04470427). Binding antibody (bAb) responses against SARS-CoV-2 variants of interest and COVID-19 incidence after vaccination were also evaluated. Median boosting interval was 315 days. The mRNA-1273 booster was well-tolerated, with an acceptable safety profile. Relative to pre-booster, nAb geometric mean levels increased after the booster by 17.8-fold and 4.7-fold among pre-booster SARS-CoV-2-negative and -positive participants, respectively. Effectiveness was successfully inferred based on noninferiority of nAb levels from mRNA-1273 booster dose (Day 29) compared with nAb levels after mRNA-1273 primary series (Day 57) among young adults in COVE. Further, the booster increased bAb levels relative to pre-booster baseline against SARS-CoV-2 variants (alpha [B.1.1.7], beta [B.1.351], gamma [P.1], and delta [B.1.617.2]), regardless of pre-booster SARS-CoV-2 status. COVID-19 incidence (cases per 1000 person-months) was lower among boosted (0 cases) than non-boosted (95.766 cases) participants in January 2022, a peak period during the early omicron transmission. In summary, the mRNA-1273 50-μg booster induced robust nAb responses in previously vaccinated adolescents, regardless of SARS-CoV-2 serostatus. Effectiveness was successfully inferred and the booster was well-tolerated, with no new safety concerns identified.

Keywords: SARS-CoV-2; TeenCOVE; adolescents; booster dose; immunogenicity; mRNA vaccine; mRNA-1273; vaccine effectiveness.

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Conflict of interest statement

AF, WX, WD, BG, FP, JM, and RD are employees of Moderna, Inc., and hold stock/stock options in the company. KA has nothing to disclose. GB received vaccine clinical research payments for work completed for Moderna, Inc. AY and KS are consultants and were contracted by Moderna, Inc., for this study.

Figures

Figure 1.
Figure 1.
Participant disposition.
Figure 2.
Figure 2.
Neutralizing antibody concentrations against ancestral SARS-CoV-2 (D614G) in adolescent mRNA-1273 booster recipients by pre-booster SARS-CoV-2 status.
Figure 3.
Figure 3.
Local (a) and systemic (b) adverse reactions by grade within 7 days after mRNA-1273 booster.
See this image and copyright information in PMC

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