Postcard reminders from GPs for influenza vaccine: are they more effective than an ad hoc approach?

All persons 65 years and older are recommended to be immunised against influenza each autumn. As immunisation rates remain low, we conducted a randomised control trial in a three-partner urban general practice to evaluate the differential effectiveness of a single postcard reminder in a general practice setting compared to usual care. All non-residential patients aged 65 years and over were identified from the age/sex/disease register. After exclusions, 325 patients were stratified by sex (125 men and 200 women) and randomised to receive either a postcard reminder in large print mailed in April or usual care. General practitioners (GPs) were blind to the randomisation. A blinded record audit performed in July demonstrated that the postcard was effective in increasing immunisation for men (chi(2)1df = 3.85; p = 0.05) but not for women (chi(2)1df = 0.45; p = 0.50). After adjusting for 1995 immunisation status, the effect of the postcard on immunisation rates was even stronger in men (Wald chi(2)1df = 6.20; p = 0.01) but remained non-significant in women (Wald chi(2)1df = 1.38; p = 0.24). With this adjustment, the odds of having the 1996 flu vaccine for men sent the postcard reminder were three times that of men in the control group (OR = 3.0; 95% CI 1.3-6.9). In a general practice setting, a single postcard reminder appears to be a promising way to boost influenza immunisation rates among ageing men. Replication of the study is recommended.