SIREN (SARS-CoV-2 immunity and reinfection evaluation)

Project summary:

The aim of SIREN is to find out whether healthcare workers who have evidence of prior COVID-19 (detected by positive antibody tests) are protected from future episodes of infection, compared to those who do not have evidence of infection. Nearly 50,000 healthcare professionals enrolled in the existing SIREN study are given PCR tests every two weeks, as well as regular antibody blood tests. 

In August 2021, the UK Health Security Agency (UKHSA) announced £1.5 million in funding from UKRI for SIREN, together with a number of other consortia, to lead a study to understand why some people become infected after vaccination or prior infection while others do not.


National Institute of Health Research (NIHR), the UK Health Security Agency

Leader researcher:

Professor Susan Hopkins

Lead institution:

Public Health England

Vaccine type:


Recruitment for clinical trial open:



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