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

BMJ Open. 2022 Dec 30;12(12):e069065. doi: 10.1136/bmjopen-2022-069065.


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.

Trial registration number: NCT04760132.

Keywords: COVID-19; IMMUNOLOGY; Infection control.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Antibodies, Viral
  • COVID-19 Vaccines* / adverse effects
  • COVID-19* / epidemiology
  • COVID-19* / prevention & control
  • Cohort Studies
  • Denmark / epidemiology
  • Female
  • Humans
  • Immunoglobulin G
  • Male
  • Middle Aged
  • Prospective Studies
  • SARS-CoV-2
  • Vaccination


  • COVID-19 Vaccines
  • Antibodies, Viral
  • Immunoglobulin G

Supplementary concepts

  • SARS-CoV-2 variants

Associated data