HIV infection causes a loss of immunity to smallpox, even in people who were vaccinated as children and are taking antiretroviral therapy (ART) to restore their immune system, according to a study published in the Journal of Infectious Diseases. The loss of immunity, also referred to as “HIV-associated immune amnesia,” could be related to why people with HIV who are on ART still have shorter lives on average than people without HIV, the study noted.  

One hundred HIV-positive and HIV-negative women who were vaccinated against smallpox in their youth were evaluated in the study. The participants’ blood was exposed to the vaccinia virus, which is used in the smallpox vaccine, in order to assess T-cell and antibody responses.

Typically, a person vaccinated against smallpox has CD4 T-cells that remember the virus and respond in large numbers when the person is exposed to it again; however, the immune systems analyzed in the HIV-positive women on ART had a limited response to the vaccinia virus.

The researchers suggest that although ART may increase total T-cell counts, it cannot recover virus-specific T-cells created by childhood vaccinations.

The next steps include evaluating whether the loss of smallpox immunity also occurs in HIV-infected men and whether people with HIV also lose immune memory to other diseases.


HIV triggers immune system ‘amnesia’ to smallpox: study. US News. Published January 9, 2020. Accessed January 13, 2020.