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A new study suggests that receiving a vaccine after an outbreak of the herpes zoster virus, which causes shingles, does not decrease the risk of shingles-associated stroke.
Researchers from the U.S. Centers for Disease Control and Prevention (CDC) presented the findings at this month’s 2019 International Stroke Conference, indicating that the effects of Zostavax and antiviral treatments do not reduce the risk of shingles-associated strokes. An abstract for the study was issued this month by the medical journal Stroke, but the full findings have not yet been published for peer review.
Zostavax is a single-dose shingles vaccine, which is typically administered before a shingles outbreak. Antiviral treatments are generally given after an outbreak has occurred. However, researchers looked at whether giving Zostavax by itself, or with antiviral treatment, after a shingles diagnosis helped lower the risk of strokes.
CDC researchers looked at data on more than 35,000 Medicare fee-for-service beneficiaries age 66 and older who were diagnosed with herpes zoster (HZ) or acute ischemic stroke (AIS) from 2007 through 2015. They looked at the association between the two conditions and estimated the incident rate ration. They classified beneficiaries into four groups: no vaccination and no antiviral treatment, vaccination only, antiviral treatment only, and both vaccination and antiviral treatment.
The study only looks at Zostavax as a vaccine. The other shingles vaccine, Shingrix, was not approved until 2017, after the study period had ended.
According to the findings, there was no evidence that either Zostavax or antiviral treatment lowered the risk of stroke, while in the same study, the researchers confirmed a “pattern of association” between shingles and the risk of stroke. That risk was consistent across age groups, sex, and race.
“Risk of AIS increased significantly following HZ, and this increased risk didn’t appear to be modified by HZ vaccination and antiviral treatment following HZ,” the researchers determined. “Primary prevention of HZ by HZ vaccination might be the most effective approach to prevent HZ-associated AIS.”
The findings come as Merck faces a growing number of Zostavax lawsuits filed in courts throughout the U.S., each involving similar allegations that the manufacturers of that older shingles vaccine failed to warn consumers and the medical community that the live-virus contained in the injection was not sufficiently weakened to prevent re-activation of the dormant virus in some users.
According to allegations raised in the complaints, following inoculation with the Zostavax shingles vaccine, users may develop a more severe and persistent version of shingles, or other complications, including Guillain-Barre syndrome, acute disseminated encephalomyelitis (ADEM), transverse myelitis, meningitis, facial paralysis, vision problems and other injuries.