First occurrence of virologically confirmed (by PCR to SARS-CoV-2), symptomatic mild, moderate or severe COVID-19 with onset at least 7 days after second study vaccination (e.g., Day 28) in serologically negative (to SARS-CoV-2) adult participants at baseline until the endpoint-driven efficacy analysis is triggered by the occurrence of a prespecified number of blinded endpoints.

First occurrence of virologically confirmed (by PCR to SARS-CoV-2), symptomatic mild, moderate or severe COVID-19 with onset at least 7 days after second study vaccination (e.g., Day 28) in serologically negative (to SARS-CoV-2) adult participants at baseline until the endpoint-driven efficacy analysis is triggered by the occurrence of a prespecified number of blinded endpoints.

• FIRST PRIMARY ENDPOINT: First occurrence of virologically confirmed (by PCR to SARS-CoV-2), symptomatic COVID-19 with onset at least 7 days after second study vaccination (e.g., Day 28) in serologically negative (to SARS-CoV-2) adult participants at baseline until the endpoint-driven efficacy analysis is triggered by the occurrence of a prespecified number of blinded endpoints. • SECOND PRIMARY ENDPOINT: First occurrence of virologically confirmed (by PCR to SARS-CoV-2), symptomatic moderate or severe COVID-19 with onset at least 7 days after second study vaccination (e.g., Day 28) in serologically negative (to SARS-CoV-2) adult participants at baseline until the endpoint-driven efficacy analysis is triggered by the occurrence of a prespecified number of blinded endpoints.

• FIRST PRIMARY ENDPOINT: First occurrence of virologically confirmed (by PCR to SARS-CoV-2), symptomatic COVID-19 with onset at least 7 days after second study vaccination (e.g., Day 28) in serologically negative (to SARS-CoV-2) adult participants at baseline until the endpoint-driven efficacy analysis is triggered by the occurrence of a prespecified number of blinded endpoints. • SECOND PRIMARY ENDPOINT: First occurrence of virologically confirmed (by PCR to SARS-CoV-2), symptomatic moderate or severe COVID-19 with onset at least 7 days after second study vaccination (e.g., Day 28) in serologically negative (to SARS-CoV-2) adult participants at baseline until the endpoint-driven efficacy analysis is triggered by the occurrence of a prespecified number of blinded endpoints.