One of the updated Cochrane Reviews from October 2023 is the third update of a review of the effects of vaccines for Herpes Zoster. It was conducted by a team of researchers in Brazil and we asked one of the authors, Juliana Gomes from the Department of Geriatrics and Gerontology at the Federal University of São Paulo, to describe its importance and main findings.
Mike: Hello, I'm Mike Clarke, podcast editor for the Cochrane Library. One of the updated Cochrane Reviews from October 2023 is the third update of a review of the effects of vaccines for Herpes Zoster. It was conducted by a team of researchers in Brazil and we asked one of the authors, Juliana Gomes from the Department of Geriatrics and Gerontology at the Federal University of São Paulo, to describe its importance and main findings.
Juliana: Herpes Zoster or shingles is a neurocutaneous disease characterized by the reactivation of the zoster varicella virus, which is the same virus responsible for chickenpox.
When the chickenpox episode is over, the virus can remain dormant inside the person´s spinal nerves, where it does not replicate because of the specific immunity that the person acquired. However, if that immunity declines for any reason, the virus may reactivate and travel through the nerve to the skin, producing clusters of blisters along the path of the affected nerve. This condition is called herpes zoster or shingles, and it can be extremely painful with symptoms such as itching, numbness, tingling and localized pain that can occur before skin lesions appear. The severe pain suffered by some patients with shingles is caused by inflammation of the sensory nerves, and this pain, as well as the other symptoms, have an important impact on patients’ quality of life.
As people get older, their specific immunity to the varicella zoster virus tends to decline and the virus can start to replicate again. That is why elderly people have a higher risk of developing shingles, and its incidence increases with advancing age. However, vaccines can prevent shingles and our Cochrane Review provides an up-to-date estimate of its effects, confirming the findings of the previous version, which was published in 2019.
Currently, there are two types of shingles vaccines. One is the single-dose live attenuated zoster vaccine (or LZV). This contains the same live attenuated virus used in the varicella vaccine but has 14 times more plaque-forming units of the attenuated virus per dose. The other is the recombinant zoster vaccine (or RZV), which does not contain the live attenuated virus, but rather a small fraction of the virus that cannot replicate but can increase immunogenicity. The recommended schedule for RZV is two doses, two months apart.
Our updated review now includes a total of 26 studies involving just over 90,000 healthy older adults with a mean age of nearly 64. Sixteen studies tested LZV and ten tested RZV. Only three studies evaluated the cumulative incidence of herpes zoster in groups receiving vaccines versus placebo. Most studies were conducted in high-income countries in Europe and North America and included healthy Caucasians (understood as white participants) aged 60 years or older without immunosuppressive comorbidities. Two studies were conducted in Japan and one was conducted in the Republic of Korea.
Based on this evidence, we found that single dose LZV and two doses of RZV are both likely to be effective in preventing shingles for at least three years but, to date, there are no data to recommend revaccination after a person receives the basic schedule of the vaccine. On the negative side, both vaccines produce systemic and injection site adverse events of mild to moderate intensity.
In conclusion, our review continues to show that existing vaccines probably prevent herpes zoster in older adults. However, the results of ongoing trials may add more relevant data to this interesting and important area of research.
Mike: To read this latest update of the Cochrane review, and to watch for further updates as extra evidence becomes available, visit Cochrane Library dot com and run a search for 'vaccines for herpes zoster'.