The value of the flu shot in elderly people relies heavily on the mental state of the person, a new British study suggests.

Researchers at the University of Birmingham’s School of Sport and Exercise Sciences found that one month after receiving the flu shot, bereaved elderly showed a 69% lower antibody response to one flu strain and an 83% lower response to a second strain. Unmarried participants had a 74% lower antibody response to one strain of flu, compared to those who were happily married.

While it is difficult to change someone’s bereavement or marital status, there are measures, such as counseling, to help people cope more effectively, said study lead author Anna C. Phillips. These measures might help improve a person’s emotional and physical well being. For elderly in nursing homes, a flu shot cuts the risk of death by 75%-80%, according to the National Institutes of Health.