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Study Shows Smallpox Vaccine Effective in HIV Patients, Boosters May Be Needed
A recent study published in the Journal of Medical Virology reveals that the smallpox vaccine, JYNNEOS, effectively induces immunity against mpox virus infection, formerly known as simian smallpox, in patients with human immunodeficiency virus (HIV). However, patients with lymphocyte counts below 500 cells/mm3 may require booster doses to maintain efficient immune responses.
The study, conducted by researchers at the Infection Biology Laboratory of the Department of Medicine and Life Sciences at Pompeu Fabra University and the HIV Unit of the Hospital del Mar Medical Research Institute in Barcelona, Spain, analyzed T-cell responses induced by vaccination with JYNNEOS. The vaccine, approved by the US Food and Drug Administration and the European Medicines Agency, provides protective cross-reactivity against orthopoxviruses, including smallpox and mpox.
Despite a significant decrease in the frequency of mpox cases globally, the virus continues to circulate, posing a threat due to the absence of a specific vaccine. During the 2022 outbreak in the United States and Europe, vaccine shortages prompted the emergency use authorization of a lower intradermal dose to increase vaccine supply.
The study, which included outpatient HIV-infected individuals receiving antiretroviral therapy, evaluated vaccine responses in patients with CD4+ T-lymphocyte counts ≤ 500/mm3 (loCD4 group) or ≥ 500/mm3 (hiCD4 group) compared to vaccinated controls without HIV. Results showed that the intradermal dose-saving vaccination route was preferable, and patients in the loCD4 group may require at least one booster to generate an efficient T-cell response against mpox.
Dr. Robert Güerri-Fernandez, head of infectious diseases at the Hospital del Mar Medical Research Institute and lead author of the study, emphasized the importance of booster doses for patients with HIV who do not exhibit an adequate immune response. Further research is needed to evaluate responses to JYNNEOS vaccination and compare different administration routes in this population.
While the study builds knowledge on vaccine effectiveness, infectious disease specialist Dr. Julián García from the Huésped Foundation in Buenos Aires, Argentina, highlighted the need for larger studies with control groups from all administration routes and immune correlates of protection.
Despite limitations, the study underscores the potential of the smallpox vaccine in protecting vulnerable populations against mpox. With ongoing research, efforts to optimize vaccine strategies and monitor immune responses aim to enhance protection against infectious diseases in individuals with HIV.
