London School of Hygiene & Tropical Medicine

Public Health England have announced that the seasonal influenza vaccine has provided low protection this winter against flu infection caused by one particular subtype, H3N2. This is because of a mismatch between the A(H3N2) strain selected for the vaccine this year and the main A(H3N2) strain that has been circulating in the UK this winter.

Commenting on this, Dr Marc Baguelin, Mathematical Modeller and Health Economist at the London School of Hygiene and Tropical Medicine, said: "One key component of the design of the UK selective immunization programme against influenza has been to look at its long-term effect. For this, the benefit of the vaccine in terms of protection provided to the population over several seasons is compared against the cost of this vaccine. In the long term, it has been shown to be highly cost-effective. This means that the benefits (in term of reducing influenza episodes, hospitalisations and deaths in the UK population) exceed greatly the cost of the vaccine. This remains true in the long term, despite some seasons (like this one) presenting low activity or poor match of one vaccine strain compared to the circulating strains.

"Given the unpredictable nature of influenza virus dynamics, flu vaccination is the best intervention we have at the moment to prevent deaths and hospitalisations through direct or indirect protection. Additionally, vaccines usually aim at providing protection against three or four different strains, so, even in a year where there is a mismatch between one of the vaccine strains and one of the circulating strains, the vaccine still gives protection against the other strains."