HIV-positive patients have a good response to vaccination against hepatitis A virus, US investigators report in the June 15th edition of the Journal of Infectious Diseases. Overall, 85% of patients who had an initial response to the vaccination remained protected against the infection six to ten years later.
“HIV-infected adults achieve high initial seroconversion rates after hepatitis A vaccination with most initial responders maintaining seropositive responses for up to 6-10 years,” comment the investigators.
A low HIV viral load was associated with a good response to the vaccine. However, the investigators also found that overall response rates were poorer in patients with HIV than in the general population.
Hepatitis A virus can cause unpleasant, sometimes serious, symptoms and it is recommended that all patients with HIV should be immunised against the infection.
The vaccine is provided in two doses and studies conducted in HIV-negative individuals have shown that there is a 100% initial response rate, and that the vaccine continues to provide protection in the long term.
However, little is known about the long-term efficacy of the vaccine in HIV-positive patients.
Therefore, investigators from the US Military HIV Natural History Study conducted a retrospective analysis of vaccine response in 130 HIV-positive patients. The patients received the vaccine between 1996 and 2003 and were followed until 2007.
All individuals had their response to vaccine assessed after one and three years. Where available, data on longer-term responses (six to ten years) were also analysed. An antibody concentration of 10 miu/ml was considered protective against the infection.
The researchers also compared the rates of protection achieved in patients with HIV with those observed in HIV-negative.
Most (96%) of the HIV-infected patients were male, their median age was 35 years, and 51% were Caucasian. Hepatitis B co-infection was present in 9% of patients, and 2% were co-infected with hepatitis C.
When the first dose of the vaccine was provided, the patients had a median CD4 cell count of 461 cells/mm3 and 49% had a viral load below 1000 copies/ml. A total of 81 patients (62%) were taking HIV therapy, and 63% of these individuals had a viral load below 1000 copies/ml.
Twelve-months after vaccination, 89% of patients were protected against hepatitis A infection. Most (90%) of these patients were still protected after three years, and 85% still had adequate antibody levels after six-to-ten years.
Individuals with a CD4 cell count above 350 cells/mm3 at the time of vaccination were more likely to have an initial response than those with lower CD4 cell counts (94% vs. 78%, p = 0.006). Response rates for individuals with a CD4 cell count of 350 cells/mm3 or above were still higher (but not significantly so) after three years (95% vs. 87%), but there was no difference in response according to CD4 cell count in the longer term.
For patients who had an initial response, mean antibody levels at years one, three, and six-to-ten were 154, 111, and 64 miu/ml respectively.
Further analysis showed that a viral load below 400 copies/ml was associated with higher antibody concentrations in the long term (p = 0.02)
A CD4 cell count above 350 cells/mm3 and a viral load below 1000 copies/ml were associated with more robust concentrations of antibodies at all time points. Moreover, further analysis showed that a viral load below 400 copies/ml was associated with higher antibody levels in the long term (p = 0.02).
However, antibody concentrations were lower in HIV-positive patients than in the HIV-negative controls, all of whom had an initial response to the vaccination.
“Given the lower initial antibody levels and increasing life expectancy of HIV-infected persons, postvaccination booster doses may be necessary to maintain anti-hepatitis A virus levels > 10 miu/ml over time (ie, > 10 years),” write the authors.
They conclude, “maintaining suppressed HIV RNA levels among HIV-infected persons may be an important strategy for sustaining durable antibody levels for vaccine preventable infections such as hepatitis A virus.”
Crum-Cianflone NF et al. Long-term durability of immune responses after hepatitis A vaccine among HIV-infected adults. J Infect Dis 203: 1815-23, 2011 (click here for the free abstract).