Flu Shot Cuts Infection Risk in UK Healthcare Workers

TOPLINE:

Among UK healthcare workers, seasonal flu vaccination substantially lowered the risk for infection during the winter of 2023-2024, and vaccinated staff recorded fewer positive influenza tests than their unvaccinated peers.

METHODOLOGY:

• Researchers in England conducted a prospective cohort study to determine the vaccine effectiveness against influenza infection in 4934 UK healthcare workers (median age, 55 years; 78.7% women; 85.6% White) between September 2023 and March 2024.
• Participants submitted respiratory swabs for influenza testing and completed online questionnaires every fortnight; status of seasonal influenza vaccination was confirmed via follow-up questionnaires and linked national registry data.
• The primary outcome was polymerase chain reaction (PCR)-positive influenza infection; the secondary outcome was symptomatic influenza infection within 7 days before or after the PCR-positive sampling date.
• The median follow-up duration per participant was 156 days.

TAKEAWAY:

• Overall, 78.2% of participants received influenza vaccination, of whom 5.4% tested positive for influenza, with 4.6% among those tested at least 14 days after vaccination and 8.1% among those unvaccinated or tested fewer than 14 days after vaccination.
• Vaccine effectiveness was 39.9% (95% CI, 21.8-53.8) against all influenza infections and 38.7% (95% CI, 18.4-53.9) against symptomatic cases, with similar effectiveness observed for both case-control and test-negative case-control analyses.
• Vaccinated participants were more likely to be aged 65 years or older (8.7% vs 3.8%), men (22.6% vs 16.9%), and White (87.4% vs 79.1%) and have a chronic disease or immunosuppression (28.7% vs 20.7%) than unvaccinated participants.

IN PRACTICE:

“The findings of this study, the largest to our knowledge to estimate influenza VE [vaccine effectiveness] in HCWs [healthcare workers], emphasise the ongoing importance of routine seasonal influenza vaccination of this occupational group,” the authors wrote.

“Efforts to increase influenza vaccine uptake in HCWs are likely to require a multifaceted approach that includes a focus on supply of and access to vaccines, as well as educational approaches to address existing concerns,” they added.

SOURCE:

This study was led by Luke J. McGeoch, Field Service South-East and London, Chief Medical Advisor’s Group and Field Epidemiology Training Programme of the UK Health Security Agency, London, England. It was published online on August 12, 2025, in Journal of Infection.

LIMITATIONS:

The 14-day interval between successive swabs may have resulted in missed infections that arose and cleared between tests. Vaccine effectiveness by influenza types and subtypes could not be assessed due to unavailable data, and the study had limited statistical power for subgroup analyses.

DISCLOSURES:

This study was supported by the UK Health Security Agency and the UK Department of Health and Social Care, with contributions from governments of Northern Ireland, Scotland, and Wales; the National Institute for Health Research; UK Research and Innovation’s UK Medical Research Council; and others. The authors declared having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.