Cohort Profile:The Danish National Cohort Study of Effectiveness and Safety of SARS-CoV-2 vaccines (ENFORCE)

Nina Breinholt Stærke*, Joanne Reekie, Isik S Johansen, Henrik Nielsen, Thomas Benfield, Lothar Wiese, Ole S Søgaard, Martin Tolstrup, Kasper Karmark Iversen, Britta Tarp, Fredrikke Dam Larsen, Lykke Larsen, Susan Olaf Lindvig, Inge Kristine Holden, Mette Brouw Iversen, Lene Surland Knudsen, Kamille Fogh, Marie Louise Jakobsen, Anna Katrin Traytel, Lars OstergaardJens Lundgren, ENFORCE Study Group, Thomas Benfield (Member of study group), Louise Krohn-Dehli (Member of study group)

*Corresponding author for this work
6 Citations (Scopus)


PURPOSE: The ENFORCE cohort is a national Danish prospective cohort of adults who received a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine as part of the Danish National SARS-CoV-2 vaccination programme. It was designed to investigate the long-term effectiveness, safety and durability of SARS-CoV-2 vaccines used in Denmark.

PARTICIPANTS: A total of 6943 adults scheduled to receive a SARS-CoV-2 vaccine in the Danish COVID-19 vaccination programme were enrolled in the study prior to their first vaccination. Participants will be followed for a total of 2 years with five predetermined follow-up visits and additional visits in relation to any booster vaccination. Serology measurements are performed after each study visit. T-cell immunity is evaluated at each study visit for a subgroup of 699 participants. Safety information is collected from participants at visits following each vaccination. Data on hospital admissions, diagnoses, deaths and SARS-CoV-2 PCR results are collected from national registries throughout the study period. The median age of participants was 64 years (IQR 53-75), 56.6% were women and 23% were individuals with an increased risk of a serious course of COVID-19. A total of 340 (4.9%) participants tested positive for SARS-CoV-2 spike IgG at baseline.

FINDINGS TO DATE: Results have been published on risk factors for humoral hyporesponsiveness and non-durable response to SARS-CoV-2 vaccination, the risk of breakthrough infections at different levels of SARS-CoV-2 spike IgG by viral variant and on the antibody neutralising capacity against different SARS-CoV-2 variants following primary and booster vaccinations.

FUTURE PLANS: The ENFORCE cohort will continuously generate studies investigating immunological response, effectiveness, safety and durability of the SARS-CoV-2 vaccines.


Original languageEnglish
Article numbere069065
JournalBMJ Open
Issue number12
Publication statusPublished - 30 Dec 2022


  • COVID-19
  • Infection control


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