Comparison of Herpes Zoster Vaccines in Recent Study

Introduction to Varicella Zoster Virus

A recent study published in The BMJ examined the effectiveness and safety of a new herpes zoster vaccine compared to an older alternative. The Varicella zoster virus (VZV) is responsible for chickenpox and shingles in humans. Chickenpox primarily affects children, leading to itchy blisters that facilitate viral transmission. Importantly, recovering from chickenpox does not guarantee immunity against subsequent VZV infections. After chickenpox resolves, VZV can remain dormant in the body for many years before reactivating and causing herpes zoster, commonly referred to as shingles.

Impact of Herpes Zoster

Herpes zoster manifests as a skin condition but can also lead to acute, subacute, or chronic neurological issues. Studies indicate that approximately one in four individuals will experience herpes zoster in their lifetime, with the risk significantly heightened for those over 50 years of age. The precise mechanisms behind the virus’s reactivation and subsequent disease development remain unclear, although preventive vaccines are available.

Types of Vaccines for Herpes Zoster Prevention

Currently, two types of vaccines are available to prevent herpes zoster: live attenuated and adjuvant recombinant subunit vaccines. The live attenuated vaccine is recommended for individuals 50 years and older and is widely available in high-income countries. This vaccine works by exposing individuals to a weakened form of the virus, prompting an immune response without causing the disease. However, its effectiveness diminishes in individuals aged 70 and older and is not advised for those with compromised immune systems.

Introduction of a New Vaccine

Recently, a new adjuvant recombinant subunit vaccine was developed and approved in Canada and several other countries. This vaccine utilizes specific components of the virus rather than the whole organism to stimulate an immune response. Subunit vaccines tend to be cheaper, easier to produce, and associated with fewer side effects, although they may not be as effective as live attenuated vaccines.

Study Findings on Vaccine Effectiveness

The emergence of two herpes zoster vaccines has sparked discussion about their relative effectiveness. Researchers conducted a comprehensive analysis comparing the two vaccines, with their findings published in The BMJ. The study involved a review of existing literature, identifying 27 studies—22 of which were clinical trials—to assess the effectiveness and safety of the live attenuated vaccine versus the new subunit vaccine and a placebo in individuals aged 50 and older.

The analysis concluded that the adjuvant recombinant subunit vaccine is more effective than both the live attenuated vaccine and placebo in preventing herpes zoster infection. However, the subunit vaccine was associated with a higher incidence of adverse events at injection sites compared to the live attenuated version. A limitation of the study was the insufficient data available, which hindered more in-depth analyses for a comprehensive comparison.

Remaining Questions and Future Research

While this study represents the first comprehensive comparison of the two herpes zoster vaccines, several questions remain unanswered. For instance, it is still unclear whether the subunit vaccine is more effective for individuals with compromised immune systems. Ongoing clinical trials comparing the two vaccines will contribute additional data in the future, allowing for a more updated assessment.

References

Karch, C. P., & Burkhard, P. (2016). Vaccine technologies: From whole organisms to rationally designed protein assemblies. Biochemical Pharmacology. 120, 1-14.
Kennedy, P. G. E., & Gershon, A. A. (2018). Clinical Features of Varicella-Zoster Virus Infection. Viruses. 10, (11).
Tricco, A. C., Zarin, W., Cardoso, R., Veroniki, A. A., Khan, P. A., Nincic, V., Ghassemi, M., Warren, R., Sharpe, J. P., Page, A. V., & Straus, S. E. (2018). Efficacy, effectiveness, and safety of herpes zoster vaccines in adults aged 50 and older: Systematic review and network meta-analysis. BMJ. 363.