The study randomised 40 patients aged 60 years or over, with a diagnosis of depression or a history of depression, to receive either herpes zoster vaccine or placebo. For each patient with depression, a matched control without depression was included. All participants had their varicella-zoster virus specific T-cell immunity and varicella-zoster virus antibody measured pre-vaccination, at six weeks, one year and two years.
Those with depression not using antidepressants had significantly lower levels of immunity, compared with matched control patients. At six weeks, those with depression and not taking antidepressants had a mean VZV-responder cell frequency (VZV-RCF) of 0.65, compared with 1.03 in controls. At two years this dropped to 0.52, compared with 0.84 in controls. Depressed patients on medication had significantly higher levels of VZV-RCF than unmedicated depressed patients. At six weeks they had a mean VZV-RCF of 1.02, which dropped to 0.67 at two years.
What does it mean for GPs?
The UK researchers concluded that ‘among depressed elderly persons, treatment with SSRI might increase the efficacy of zoster vaccine and, possibly, vaccines against other important pathogens, such as influenza viruses.’
Dr George Kassianos, GP in Wokingham and RCGP lead on immunisations: ‘It is a well-known fact that elderly respond less to vaccinations and this phenomenon is called immunosenescence. Prescribing an antidepressant to these individuals not only improves their quality of life but also their ability to produce antibodies after varicella zoster vaccination. The Joint Committee on Vaccination and Immunisation needs to consider lowering the age of vaccination to below 70 years, for elderly who suffer from depression.’