Effectiveness of bivalent Covid-19 booster vaccines in the Nordic countries

Study type

• Study type:
  Non-interventional study
• Scope of the study:
  Effectiveness study (incl. comparative)

Non-interventional study

• Non-interventional study design:
  Cohort

Population studied

• Age groups:
  • Adults (18 to < 46 years)
  • Adults (46 to < 65 years)
  • Adults (65 to < 75 years)
  • Adults (75 to < 85 years)
  • Adults (85 years and over)
• Special population of interest:
  Immunocompromised
• Estimated number of subjects:
  3400000

Study design details

• Main study objective:
  The aim of this project is to evaluate the comparative effectiveness of the bivalent boosters in preventing severe Covid-19 outcomes and all-cause mortality among individuals aged 50 years or older with 9 months of follow-up.
• Outcomes:
  Covid-19 hospitalisation and Covid-19 mortality.
• Data analysis plan:
  We will take advantage of the unique nationwide register-data available to us, and construct country cohorts with individual-level information on dates of vaccination and dates of effectiveness end-points together with relevant covariate information. Using target trial emulation, we will compare bivalent booster dose recipients head-to-head and with unboosted individuals in matched survival analysis that provides comparative effectiveness estimates while taking into account a range of covariates.