Recent research suggests that the protective effects of the Zostavax shingles vaccine may diminish after approximately a decade, raising concerns about its long-term efficacy.
Published this month in a medical journal, a study by researchers from Kaiser Permanente and Merck & Co. – Zostavax's manufacturer – reveals that the vaccine is only around 15% effective in preventing shingles after 10 years.
Merck introduced Zostavax in 2006 as the first U.S.-approved vaccine for shingles prevention, administered through a single-dose injection containing a live virus intended to prevent the development of this painful condition. Despite its initial purpose, several thousand Zostavax lawsuits have been filed, alleging the vaccine's ineffectiveness and potential for causing persistent shingles outbreaks, as well as various severe injuries such as neurological problems, autoimmune diseases, vision loss, and hearing damage.
In the latest study, researchers analyzed data from over 1.5 million people aged 50 or older within the Kaiser Permanente Northern California healthcare system from 2007 to 2018. They assessed vaccine effectiveness against shingles, postherpetic neuralgia, herpes zoster ophthalmicus, and hospital admissions for shingles.
The findings indicate that even after the initial injection, Zostavax was only 67% effective in preventing shingles, with efficacy dropping to 15% after a decade. Similar declines were observed in the vaccine's protection against related conditions, such as postherpetic neuralgia (from 83% to 41%), herpes zoster ophthalmicus (from 71% to 29% between five and eight years post-injection), and hospital admissions for shingles (from 90% to 53% between five and eight years).
As Merck faces product liability lawsuits alleging withholding of critical information about Zostavax's potential side effects and exaggeration of its effectiveness, the research findings may impact ongoing litigation.
All Zostavax lawsuits have been consolidated in a federal multidistrict litigation (MDL) before a U.S. District Judge in the Eastern District of Pennsylvania, reflecting shared concerns and legal issues across the cases.