Phase 1: • Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Phase 2/3 Primary Safety: Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Primary Immunogenicity: •SARS-CoV-2 neutralizing titers

Phase 1: • Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Phase 2/3 Primary Safety: Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Primary Immunogenicity: •SARS-CoV-2 neutralizing titers

Phase 1: • Participants 16 to <30, 12 to <16, ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Phase 2/3 Primary Safety: Participants 16 to <30, 12 to <16, ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Primary Immunogenicity (Selected dose): •SARS-CoV-2 neutralizing titers

Phase 1: • Participants 16 to <30, 12 to <16, ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Phase 2/3 Primary Safety: Participants 16 to <30, 12 to <16, ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Primary Immunogenicity (Selected dose): •SARS-CoV-2 neutralizing titers

Phase 1: • Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Phase 2/3 Primary Safety: Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Primary Immunogenicity: •SARS-CoV-2 neutralizing titers

Phase 1: • Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Phase 2/3 Primary Safety: Participants ≥5 to <12 years and ≥2 to <5 years of age: • Local reactions (pain at the injection site, redness, and swelling) • Systemic events (fever, fatigue, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) • AEs • SAEs Participants ≥6 months to <2 years of age: • Local reactions (tenderness at the injection site, redness, and swelling) • Systemic events (fever, decreased appetite, drowsiness, and irritability) • AEs • SAEs Primary Immunogenicity: •SARS-CoV-2 neutralizing titers