Substudy A - Please refer to Section 10.7.3. of the Protocol. Substudy B Primary Safety - Troponin I level - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Substudy C Primary Efficacy - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Primary Immunogenicity - SARS-CoV-2 neutralizing titers Substudy D: - Please refer to Section 10.10.3 of the Protocol. Substudy E - Please refer to Section 10.11.3. of the protocol. Substudy F - Please refer to Section 10.12.3. of the protocol.

Substudy A - Please refer to Section 10.7.3. of the Protocol. Substudy B Primary Safety - Troponin I level - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Substudy C Primary Efficacy - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Primary Immunogenicity - SARS-CoV-2 neutralizing titers Substudy D: - Please refer to Section 10.10.3 of the Protocol. Substudy E - Please refer to Section 10.11.3. of the protocol. Substudy F - Please refer to Section 10.12.3. of the protocol.

Substudy A Primary Efficacy Confirmed COVID-19 incidence from 7 days after the booster dose per 1000 person-years of blinded follow-up Primary Safety - AEs - SAEs Substudy B Primary Safety - Troponin I level - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Substudy C Primary Efficacy - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Primary Immunogenicity - SARS-CoV-2 neutralizing titers

Substudy A Primary Efficacy Confirmed COVID-19 incidence from 7 days after the booster dose per 1000 person-years of blinded follow-up Primary Safety - AEs - SAEs Substudy B Primary Safety - Troponin I level - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Substudy C Primary Efficacy - Local reactions (pain at the injection site, redness, and swelling) - Systemic events (fever, fatigue/tiredness, headache, chills, vomiting, diarrhea, new or worsened muscle pain, and new or worsened joint pain) - AEs - SAEs Primary Immunogenicity - SARS-CoV-2 neutralizing titers