UKHSA's flagship SIREN study enters new phase to continue surveillance of respiratory pathogens

The next phase of the study will be known as SIREN 2.0 and began in September 2023.

Established at the height of the pandemic in June 2020, the SARS-CoV-2 immunity and reinfection (SIREN) study has continually tested healthcare workers across the UK for COVID-19, providing crucial information relating to the virus. The evidence it has collected on immunity, vaccination and emerging variants played a critical role in informing the national response.

The SIREN study introduced testing for influenza and respiratory syncytial virus (RSV) for healthcare workers, to help gather an understanding of the impact of these viruses on winter pressures in healthcare in winter 2022 and this will continue this year.

The emergence of the BA.2.86 variant has resulted in the autumn vaccine campaign being brought forward. SIREN 2.0 testing of healthcare workers, a cohort eligible for the vaccine, will help provide answers on vaccine efficacy against this new variant, other circulating variants and infection-acquired immunity.

SIREN 2.0 will recruit participants from our original cohort of 45,000 healthcare workers, which remains the largest study of its kind globally, and we have expanded our collaborations with the Wellcome Sanger Institute and the Worldwide Influenza Centre (WIC) at the Francis Crick Institute to ensure we continue to address important scientific questions.

Susan Hopkins, Chief Medical Adviser at the UK Health Security Agency (UKHSA), said:

Thank you to all of our participants who make this crucial study possible. It is because of you that we have been able to collect vital data and insights on COVID-19 across the pandemic, furthering our understanding on immune response and the protection offered by vaccines.

This new phase of the study – SIREN 2.0 – will allow us to play a core role in the continued surveillance of COVID-19, including the detection of emerging new variants, while we will also utilise multiplex testing to assess the impact of influenza and RSV on healthcare workers.

I am delighted that we will be working with new partners from WIC and the Respiratory Virus and Microbiome Initiative (RVI) at the Wellcome Sanger Institute as we continue to answer the most important questions on the impact of respiratory diseases."

The Wellcome Sanger Institute will sequence samples provided by UKHSA and use metagenomics to investigate other pathogens that cause respiratory infection such as parainfluenza. Meanwhile, we plan to share influenza virus strains identified during the study with WIC, and these may be used to design influenza vaccines for future seasons.

Dr Ewan Harrison, Head of RVI at the Wellcome Sanger Institute, said:

We are excited to be working with the SIREN study team to maximise the yield of science that can be done using the samples taken from the SIREN participants, which provide a unique opportunity to study respiratory virus infections in healthcare workers.

The RVI builds on the technology used for the genomic surveillance of SARS-CoV-2 during the pandemic. We hope that by expanding the range of respiratory viruses that are routinely sequenced, we can contribute to scientific understanding that will help prevent and treat infections caused by respiratory viruses."

Blood samples from SIREN participants are already being tested in partnership with UKHSA's newly established Vaccine Development and Evaluation Centre (VDEC) to understand the immune response provided by vaccination against new variants, including BA.2.86, providing vital evidence to inform the national risk assessment.

The team will continue to assess the durability of protection of vaccination in our healthcare worker cohort, and will provide regular updates to experts, including the JCVI, and policymakers on the latest findings.