The team behind the SIREN study has estimated that COVID-19 infections among patient facing hospital workers would have been 69% higher without rapid vaccination during England’s second wave of the pandemic. This equates to 9.9% more of this group becoming infected.
Reporting their work in the BMJ, they concluded that the rapid vaccine rollout from December 2020 averted infection in a large proportion of such workers in England.
The SIREN study was established early on in the pandemic to monitor COVID-19 infections and the immune response in healthcare workers. The study has engaged with almost 45,000 participants across the UK who provide regular samples for testing, making SIREN the largest study of its kind anywhere in the world.
In this paper, the team set out to establish the number of first infections in hospital healthcare workers in England during the second wave (1 September 2020 and 30 April 2021), as well as to identify risk factors and the impact of the vaccine rollout. Participants were either clinical, support or administrative staff and had no evidence of previous infection.
Overall, 13% of the cohort caught COVID-19 in this period. Infections peaked in late December 2020 and decreased from January 2021, coinciding with the rapid vaccination of this group and a national lockdown.
The team identified the factors contributing to infection risk during the second wave as being:
- working in an emergency department or inpatient ward (increased risk by 21%)
- being under 25 years old (increased risk by 20%)
- having frequent exposure to patients with covid-19 (increased risk by 19%)
- being a healthcare assistant (increased risk by 18%)
- living in a large household (increased risk by 16%)
Time to first vaccination was strongly associated with infection, with each additional day of waiting multiplying a person’s risk ratio by 1.02.27% of the cohort had received a first dose of vaccine by 31 December 2021, 88% by 31 January 2021, and 96% by 30 April 2021.
Vaccine rollout was quickest among doctors and staff working in intensive care settings or in theatres. It was slowest among administrators, office-based staff and participants of black ethnicity.
The peak incidence of infections was highest in the East of England, London, and South East regions, which all had the earliest rise in circulation of the Alpha variant.
The team used mathematical modelling to estimate the impact of the vaccines on all patient facing hospital workers, including those that had already been infected prior to the second wave (estimated to be 28%). Their model indicated that, without vaccines, the rate of infection would have been 69% higher, equating to 9.9% more of the workforce becoming infected.
In conclusion, the research team stressed that ensuring equitable delivery of vaccines to healthcare workers is essential, particularly bearing in mind the need for booster doses to provide ongoing protection from the Omicron variant.
They also emphasised the need for a better understanding of the dynamics of transmission among healthcare workers, to help optimise infection control measures.
Another research paper reported in the BMJ found no difference in effectiveness between the AstraZeneca and Pfizer vaccines for health and social care workers in England.