More than 99% of people aged 40 or older in the US carry the dormant chickenpox virus, also known as the varicella-zoster virus. Shingles is a re-activation of the chicken pox virus and typically occurs after age 50. The risk of developing shingles, a painful condition that causes skin blisters and can have serious complications, increases with age and other health conditions.
“One in three people who have had chickenpox develop shingles in their lifetime,” said Dr Quanhe Yang, lead study author and senior scientist at the US Centres for Disease Control and Prevention (CDC) in Atlanta, Georgia. “The Zoster Vaccine Live helps to prevent shingles and reduces the risk for shingles by about 51%. But its effect declines with increased age, about 64% in people 60-69 years, about 41% for ages 70-79 years and about 18% in those 80 years or older.”
To help determine if the shingles vaccine reduces the risk of stroke, Yang and colleagues reviewed the Medicare health records of more than 1m Medicare fee-for-service beneficiaries age 66 or older who had no history of stroke and who were vaccinated with the Zoster Vaccine Live between 2008 and 2014, and followed them for an average of almost four years. That group was matched with the same number of Medicare fee-for-service beneficiaries who did not receive the shingles vaccine with the same four-year follow-up. To examine the effect of the vaccine on risk of stroke, researchers controlled for age, gender, race, medications and co-existing health conditions.
Researchers found: Receiving the shingles vaccine lowered the risk of stroke by about 16%, lowered the risk of ischemic (clot-caused) stroke by about 18% and lowered the risk of haemorrhagic (bleeding) stroke by about 12%; the vaccine’s protection was strongest among people ages 66 to 79 years; and among those under the age of 80 years, the shingles vaccine reduced the risk of stroke by nearly 20% and in those older than 80, reduced the risk by about 10%.
“The reason for increased risk of stroke after a shingles infection may be due to inflammation caused by the virus,” according to Yang.
“Approximately 1m people in the US get shingles each year, yet there is a vaccine to help prevent it,” said Yang. “Our study results may encourage people ages 50 and older to follow the recommendation and get vaccinated against shingles. You are reducing the risk of shingles, and at the same time you may be reducing your risk of stroke.”
This study was conducted when the only shingles vaccine was Zoster Vaccine Live (available since 2006). The newest shingles vaccine, Adjuvanted, Non-Live Recombinant Shingles Vaccine (available since 2017), confers even greater protection and is now the preferred vaccine recommended by the CDC’s Advisory Committee on Immunisation Practices. Two doses of Adjuvanted, Non-Live Recombinant Shingles Vaccine is more than 90% effective at preventing shingles and is recommended for adults age 50 and older.
Future studies are needed to confirm the link between Zoster Vaccine Live and stroke and to determine any association between Adjuvanted, Non-Live Recombinant Shingles Vaccine and risk for stroke.
Introduction: Herpes zoster (HZ) is associated with increased risk of stroke, and Zoster Vaccine Live (ZVL) reduces risk of HZ. No study examined the association between ZVL and risk for stroke. The present study examined this association among US older population.
Methods: We included 1,382,051 Medicare fee-for-service beneficiaries age ≥66 years without a history of stroke and who received ZVL during 2008-2014, and 1,382,051 matched controls (using a comprehensive list of matching variables) without ZVL followed from ZVL receipt to December 31 2016. We used Cox proportional hazard models to examine the association between ZVL and composite fatal/non-fatal incident stroke outcomes.
Results: During a median of 3.9 years follow-up (interquartile range 2.7-5.4), we documented 42,267 stroke events including 33,510 acute ischemic strokes (AIS) and 4,318 hemorrhagic strokes among beneficiaries who received ZVL over 5,890,113 person years. The corresponding numbers for controls were 48,139, 39,334, and 4,713 during 5,693,943 person years. Crude incidence comparing beneficiaries with and without ZVL were 7.18 vs. 8.45 per 1000 person years for all stroke, 5.40 vs. 6.53 for AIS, and 0.73 vs. 0.82 for hemorrhagic stroke (p<0.001 for difference). Adjusted hazard ratios comparing beneficiaries with ZVL to controls were 0.84 (95% CI 0.83-0.85), 0.82 (0.81-0.83), and 0.88 (0.84-0.91) for all stroke, AIS and hemorrhagic stroke respectively. The association between ZVL and risk for stroke appeared to be stronger among beneficiaries 66-79 years compared to those ≥80 years of age (p=0.020 for interaction), but largely consistent across sex, and racial groups.
Conclusion: Among Medicare beneficiaries, receipt of ZVL was associated with lower incidence of stroke. Further study is needed to confirm our findings.
Quanhe Yang, Anping Chang, Xin Tong, Robert Merritt