OHSU-Led Study Reveals HIV Patients Lose Smallpox Immunity Despite Vaccination When Young

HIV Preventative Drug Not Tested On nor Approved for Female Patients

A recent study led by Oregon Health & Science University reveals that HIV patients lose immunity to small pox, despite having been vaccinated against the disease in childhood, and in fact, had much of their immune system restored with anti-retroviral therapy.

Published in the Journal of Infectious Diseases, the team found that HIV-associated immune amnesia could possible represent an explanation why those living with HIV may still tend, on average, to live less years than their HIV-negative counterparts, despite the acceptance of antiretroviral therapy.


The study was led by Mark K. Slifka, Oregon Health & Science University, and his colleagues who compared the T-cell and antibody responses of 100 HIV-positive and HIV-negative women who were all vaccinated against smallpox in youth. Smallpox was selected as the last known case in the U.S. was in 1949, hence study participants couldn’t have been exposed to the underlying virus which could have triggered new T-cell and antibody responses.


The study team discovered that HIV-positive women’s immune systems, who also received antiretroviral therapy had a limited response when their blood was exposed to the vaccina virus, which is utilized by the smallpox virus.

As what would be expected in a normal situation, the individuals vaccinated against smallpox would have CD4 T cells that remember the virus and respond in large number when the exposure happens again. In fact, some previous research found that smallpox virus-specific CD4 T cells are maintained by the body for up to 75 years post-vaccination. However, this finding occurred even through the antiretroviral therapy works by increasing CD4 T cell counts in HIV-impacted patients.


What his study team found indicates that although antiretroviral therapy can boost total T cell counts, it cannot recover virus-specific T cells produced from prior childhood vaccinations.

Next Steps

The team now plans to consider a study testing if the same phenomenon happens in HIV-infected men and if people living with HIV may also lose immune memory to other diseases.


·         NIH Public Health Services grant

·         Oregon National Primate Research Center


·         OHSU, SUNY Downstate

·         Georgetown University

·         Cornell University

·         University of Southern California

·         John Hopkins University

Lead Research/Investigator

Mark K. Slifka, Oregon Health & Science University