London School of Hygiene and Tropical Medicine

Academic Institute

Charlotte Warren-Gash - Chief Investigator - London School of Hygiene & Tropical Medicine ( LSHTM )Jennifer Davidson - Corresponding Applicant - London School of Hygiene & Tropical Medicine ( LSHTM )Amitava Banerjee - Collaborator - University College London ( UCL )Clémence Leyrat - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )Emily Herrett - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )Helen McDonald - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )Ian Douglas - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )Liam Smeeth - Collaborator - London School of Hygiene & Tropical Medicine ( LSHTM )

CPRD16

In the days after severe influenza infection, people are at higher risk of an acute cardiovascular event, such as a heart attack or stroke. Influenza vaccine can prevent influenza infection or reduce the severity of illness. Vaccination can, therefore, also prevent any acute cardiovascular event which may occur after infection. Clinical trials have previously shown that in people who have pre-existing cardiovascular disease (e.g., heart disease or a previous stroke), the influenza vaccine reduces the chance of further cardiovascular events. It is unknown whether the vaccine offers the same protection to people who have risk factors for cardiovascular disease (without having pre-existing cardiovascular disease), such as in those with high blood pressure.

Observational studies have identified that acute respiratory infections can trigger acute cardiovascular events, particularly myocardial infarction and stroke. In self-controlled case series (SCCS) studies, which implicitly control for the effect of fixed confounding factors using within-individual comparisons, myocardial infarction and stroke risk were elevated two- to six-fold in the days following clinically diagnosed respiratory infections and influenza-like illness, with this elevated risk remaining for up to one month. Consistent cardiovascular triggering effects have been found for laboratory-confirmed infections, including the influenza virus. Randomized controlled trials and observational studies have also demonstrated the cardiovascular benefit of the seasonal influenza vaccine. However, randomized controlled trial data is largely limited to individuals with established cardiovascular disease (CVD). While observational studies have considered the vaccine's benefit among those without a previous cardiovascular event, the benefit specifically in people with raised cardiovascular risk has not been considered. Quantifying any protective effects of influenza vaccine in people with raised cardiovascular risk, predictive of future CVD, will further understanding of the vaccine’s cardiovascular benefits and whether it is effective for primary prevention of CVD.

26/05/2021

Release