Two years ago, we launched the SARS-CoV2-Immunity and Reinfection Evaluation Study, also known as SIREN, the largest of its kind worldwide. The study is set to find answers to some of the most important questions about COVID-19.

The SIREN study monitored the infection of a large group of healthcare workers who provided samples for routine PCR and antibody testing. Analysis of these samples has helped the UK assess COVID-19 resistance, provide insight into COVID-19 re-infection and help us understand the level of protection provided by the vaccine.

The scale of the SIREN study has been astonishing. In two years, it has performed more than one million PCR tests, performed more than 400,000 blood tests, and involved approximately 45,000 participants from 135 NHS sites across the UK.

A graphic showing the numbers related to the SIREN study: 1,101,774 PCR tests, 419,212, 135 NSH trusts, 44,546 healthcare workers, 4 UK countries.

Number of tests, sites, participants and countries involved in the SIREN study. As of June 2022, the data is accurate.

We’ve helped answer some of the most important questions about COVID-19, enabling decision makers – nationally and locally – to control the spread of the disease. In our two years of research, here are the main things we learned:

How effective are previous infections and vaccines against COVID-19?

In our first year, we saw that the previous transmission of COVID-19 provided high protection against re-infection for several months during the wild-type and alpha-variant domination period. We also found that the COVID-19 vaccine was highly effective in reducing infection (both noticeable and asymptomatic) in the months following vaccination.

In our second year, we investigated the stability of immunizations after vaccination and those who were vaccinated after previous infections during the dominant period of Delta-variant.

We found evidence of reduced safety six months after giving two vaccine doses to people who had not previously had the infection, and this informed advice on setting a booster dose. We have also demonstrated the quality of immunizations of people infected with previous infections, with those who have been vaccinated later consistently having over 90% protection over long periods of time compared to those who have not been vaccinated with previous infections.

When the Omicron variant appeared in December 2021, we were protected from two doses of the vaccine or from previous infections, when a booster dose helped to restore some of this lost immunity. This research has helped to expand the booster vaccination campaign.

We’ve collaborated with immunologists from multiple academic organizations to understand why some people get re-infections and groundbreaking infections – this will be important for understanding future vaccine goals.

How can we continue our studies?

The SIREN study would not have been possible without the efforts and dedication of participants from around the UK, and we would like to thank these individuals very much. These participants are among the most challenging situations encountered by the workforce as they volunteer to go through fortnightly tests and provide quarterly blood samples while performing their day tasks at the NHS.

We would also like to thank the 135 NHS trust sites that have encouraged their staff to participate in the research, including all-important laboratories and research teams.

Our vision includes newsletters, webinars, video messages, and celebration events to keep research participants interested. We also appointed a participant-involved panel:

“The SIREN Participation Panel consists of seven SIREN study participants recruited from a wide range of professional backgrounds and positions. As a panel we meet regularly to contribute to the SIREN study’s goals, including providing open and honest feedback on its research goals and findings. Assist in activities and ensure participants’ concerns are heard. We have evaluated the opportunity to contribute to a study that has helped us make important decisions about the COVID-19 response in the UK. “

SIREN Participating Involvement Panel, June 2022

We have also developed strong multi-disciplinary collaborations with academics from leading UK research institutes, enabling us to combine epidemiological, viral, immunological, genomic and clinical skills.

What then?

We are really pleased that the SIREN study has been funded to continue the follow-up of participants in four countries until March 31, 2023. This proves how valuable SIREN is by those who are leading the COVID-19 response.

With the decline in community testing, SIREN’s surveillance role in monitoring the trend and emerging forms of infection has become increasingly important in responding to national COVID-19 responses. SIREN will play an important role throughout the coming winter when the NHS will deal with seasonal stress, influenza, seasonal viruses and consequent staff absenteeism.

For the foreseeable future, we will be committed to addressing important research questions. What is the new variant effect? What are the effects of re-infection after vaccination? What are the effects of COVID-19 vaccine booster programs?

This study would not have been possible without the efforts and dedication of many people, including participants, the NHS site, the laboratory team, and more.

A webpage to share more information about the SIREN study can now be found here.

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