New York, Nov 11 (IANS): The effectiveness of the live zoster (shingles) vaccine is highest in the first year after vaccination and then wanes substantially.

But it continues to provide some protection against shingles and its complications ten years after vaccination, even in patients with a weakened immune system, according to a study published by The BMJ.

Herpes zoster, commonly known as shingles, is a painful rash caused by the reactivation of the chickenpox virus. It's much more common among people aged 60 and older and those with a weakened immune system and can lead to disabling complications.

Live zoster vaccine was the first vaccine against shingles; over 50 million people have received it worldwide.

To address long-term effectiveness of shingles vaccine, researchers from US-based Kaiser Permanente examined data from just over 1.5 million adults aged 50.

Of these, 507,444 (34 per cent) were vaccinated during the study period from 1 January 2007 to 31 December 2018.

Among 75,135 herpes zoster cases, 4,982 (7 per cent) developed postherpetic neuralgia (lasting pain in the area of the rash); 4,439 (6 per cent) had herpes zoster ophthalmicus (rash in or around the eye); and 556 (0.7 per cent) were admitted to the hospital for herpes zoster.

For each outcome, vaccine effectiveness was highest in the first year after vaccination and decreased substantially over time.

First-year vaccine effectiveness was 67 per cent against herpes zoster infection, 83 per cent against postherpetic neuralgia, 71 per cent against herpes zoster ophthalmicus, and 90 per cent against admission to hospital for herpes zoster.

Against herpes zoster, vaccine effectiveness waned to 50 per cent in the second year, decreased to 27 per cent in the eighth year, and then to 15 per cent after 10 years. Vaccine effectiveness for herpes zoster ophthalmicus was similar.

Against postherpetic neuralgia and admission to hospital, vaccine effectiveness started higher and also waned, but continued to confer substantial protection for several years (41 per cent after 10 years for postherpetic neuralgia and 53 per cent from 5-8 years for admission to hospital).

These are observational findings, and the authors point to several challenges, including incomplete ascertainment of shingles and immunocompromised status of patients over time.

"Further research is also needed to evaluate the trajectory of vaccine effectiveness against herpes zoster and severe outcomes over time in people with chronic diseases such as those of the kidney, heart, and autoimmune system," the team said.