Vaccine effectiveness against COVID-19 infection and related hospitalization

In the present study, the researchers estimated the effectiveness of two and three doses of COVID-19 messenger ribonucleic acid (mRNA) vaccines against SARS-CoV-2 Alpha, Delta, and Omicron variant infection and related hospitalization. The study population comprised Denmark residents aged 12 years or older in a time period where either the Alpha, Delta, or Omicron variants were dominant. The team included only the first SARS-CoV-2 positive polymerase chain reaction (PCR) test of a participant. They obtained information on all laboratory-confirmed positive reverse transcription-PCR (RT-PCR) results from the Danish microbiology database (MiBa). COVID-19-related hospitalization was defined as a new hospital admission lasting at least 12 hours, occurring within two days prior to or 14 days after the diagnosis with either the SARS-CoV-2 Alpha, Delta, or Omicron variant infection.