Gram MA, Nielsen J, Schelde AB, et al. - Vaccine programs combining different Coronavirus Disease 2019 (COVID-19) vaccine types have been observed in several countries because of the recommendations to stop using the ChAdOx1 vaccine. Hence, researchers conducted this Danish nationwide population-based cohort study with the aim to attain knowledge on vaccine effectiveness (VE) of heterologous vaccine schedules against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and COVID-19–related hospitalization and death.

• Using national registry data on all Danish residents during the study period (9 February to 23 June 2021), researchers retrieved data of a total of 144,360 individuals vaccinated with the ChAdOx1 vaccine as the first dose; 136,551 of these individuals received an mRNA vaccine as the second dose.

• Findings revealed an estimated protection of 88% against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection in correlation with receiving vaccination with the combination of ChAdOx1 and an mRNA vaccine.

• During the study period, no COVID-19–related hospitalizations or deaths were observed among the individuals vaccinated with the combined vaccine schedule.