Marital happiness is key to fighting off flu, a study by university researchers has found.
The study by the University of Birmingham's School of Sport and Exercise Sciences also discovered that bereavement has a negative effect on the body's immune response to the annual flu jab.
Dr Anna Phillips, the lead investigator on the study, said: "We know that those aged over 65 are more at risk of the impact of flu, but this research shows that within that group, those that have been recently bereaved, or those that are single, divorced or widowed are more at risk that those who are in a happy marriage.
"It is especially important for these at-risk groups to get their flu jabs."
The study looked into whether stressful life events and other related factors had an effect on the immune system's response to the flu vaccination, which gives a good indication of how well the body would fight off a real attack of flu.
The research team looked at the levels of antibodies in the blood, which are produced by the body to combat disease.
The team found that those who reported having happy marriages had a much higher level of antibodies in the blood than those reporting lower marital satisfaction.
Those who had suffered a bereavement in the year prior to vaccination had a poorer response than those who had not suffered such a loss.
More than 180 pensioners from across Birmingham took part in the study, the first of its kind to examine the impact of general psychological factors on immune response to the flu jab in older adults.
Participants gave a blood sample prior to vaccination, then further samples at one month.
Dr Phillips added: "We would like to take this research further, to see whether interventions such as bereavement counselling or marriage counselling can improve the immune response in at-risk groups."