ENFORCE PLUS (A Phase IV Vaccine Study under the National Cohort Study of Effectiveness and Safety of SARS-CoV-2/COVID-19 vaccines (ENFORCE)) is an equivalence trial to evaluate the safety of the SARS-CoV-2 vaccine Johnson & Johnson/Janssen (J&J).


The primary objective of the study is to assess if the J&J SARS-CoV-2 vaccine results in a change in the number and activation of platelets and anti-PF4 level. As well as to compare whether the J&J vaccine is causing a greater activation of platelets and anti-PF4 than the mRNA vaccines.


The J&J COVID-19 vaccine has been approved by the Danish Medicines Agency for use in Denmark, however it is not currently part of the national vaccine programme.


The study was launched 2 July 2021 and will enroll 1.000 persons initiating vaccination with the vaccine from J&J. 


Participants will have 3 specific study visits and will hereafter be followed for 2 years after the vaccination similar to the ENFORCE protocol. In this way, the participants will be offered an extra close follow up on vaccine effectiveness. Safety data will be collected at study visits until 3 months after the first vaccination, as part of ENFORCE, with additional safety data collected under this protocol during the first month after vaccination.


Research samples will be collected at each study visit during the two-year follow-up.


If you have further questions regarding the study, please contact study personnel via email: enforce.rigshospitalet@regionh.dk.



This section is for Study Staff.

You can find and download ENFORCE PLUS study related document below,

  • Protocol and protocol related documents
  • Study specific logs
  • Study specific worksheets
  • Study information materials

If you have further questions regarding the study documents, please contact study personnel via email: enforce.rigshospitalet@regionh.dk

Protocol, IC, Manualer og Dokumenter


Study specific logs


Worksheets, Serious adverse event form (SAE) and Symptom Form


Study information materials