SAN FRANCISCO, CA—Hepatitis B virus (HBV) vaccine response status was not associated with post-combination antiretroviral therapy (cART) CD4 gains at 1-year among those with virologic suppression, a study concluded at IDWeek 2013.

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Noting that HBV vaccine antibody response has been associated with reduced risk of AIDS or death but that the association between HBV vaccine response status and cART outcomes has not been well studied, Kahtonna Allen, DO, MS, from the Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, MD, and the Infectious Disease Service, San Antonio Military Medical Center, Fort Sam Houston, TX, and colleagues evaluated CD4 gains post-cART according to HBV vaccine antibody response in the US Military HIV Natural History Study.

The study population is an observational cohort evaluated at seven US Department of Defense medical treatment facilities. Enrolling since 1996, the cohort includes more than 5500 participants.

Inclusion criteria were patients with documented HBV vaccination prior to cART, at least one HBV surface antibody (HBsAb) value after vaccination and before cART, no history of HBV infection, and achievement of viral load <400 copies/mL during the first year of cART.

HBV vaccine responders were defined as those with positive HBsAb prior to cART, while non-responders had negative HBsAb. Participants were further categorized by when they received their first HBV vaccination, either prior to or following HIV infection. Linear mixed regression was used to model CD4 reconstitution within the first year of cART.

In participants whose first HBV vaccine was prior to HIV diagnosis (pre-HIV group), 292/383 (76.2%) were responders and 91/383 (23.8%) were non-responders. In participants whose first HBV vaccine was after HIV diagnosis (post-HIV group), 54/101 (53.5%) were responders and 47/101 (46.5%) were non-responders.

Median CD4 count at cART initiation among the pre-HIV group was 339 (260, 444) cells/µL and did not differ by vaccine response, Dr. Allen reported. During the first year of cART, responders in the pre-HIV group increased CD4 counts by 193 (162, 277) cells/µL compared with 167 (109,225) cells/µL among non-responders (P=0.369).

Median CD4 at cART initiation among the post-HIV group was 362 (237, 464) cells/µL, which was higher among responders (+93 [24, 163] cells/µL; P=0.010). During the first year of cART, CD4 response was similar, with a median 144 (40, 207) cells/µL gained for responders and 165 (108,222) cells/µL gained for non-responders (P=0.631).

“Regression analyses showed for those vaccinated prior to HIV infection, the factors associated with CD4 cell gains included AIDS prior to cART, CD4 cell count at cART initiation, and year of cART initiation,” Dr. Allen reported. “For those vaccinated after HIV infection but prior to starting cART, the factors associated with CD4 gains included achieving a positive HBV vaccine response, year of cART initiation, and trends for AIDS diagnosis prior to cART.”