October 27, 2008
There's nothing like hearing the results of studies directly from those who actually conducted the research. In this interview, you'll meet one of these impressive HIV researchers and read his explanation of the study he presented at ICAAC/IDSA 2008.
I'm Michael Landrum. I work in San Antonio, Texas, at Fort Sam Houston, and also with the Infectious Disease Clinical Research Program from the Uniformed Services University in Bethesda, Md. We examined hepatitis B [HBV] vaccine responses in our cohort of HIV-positive individuals, of which we looked at 626 participants who had been vaccinated with hepatitis B vaccine after their HIV diagnosis.
Michael Landrum, M.D.
Why was that? Do we understand the mechanism?
It's not entirely clear, although we think it has to do with improved CD4 cell function, because hepatitis B vaccine requires your CD4 cells to be functioning well to respond to the vaccine.
I see that HAART even improved the HBV vaccine response among people who had a CD4+ cell count greater than 350.
Correct. We looked to see if HAART benefitted all patients, or specifically patients with lower CD4 cell counts. We found that it actually benefitted all patients, even those with CD4 cell counts greater than 350. Those individuals who were on HAART with higher CD4 cell counts still benefitted from being on highly active antiretroviral therapy, similar to other recent investigations that have shown people benefit from being on HAART, even at relatively preserved or high CD4 cell counts.
Do you know what the prevalence of HBV is in people with HIV?
In our cohort, if you look for any serologic evidence of hepatitis B infection, the prevalence is about 40% to 50%. For chronic hepatitis B, it's around 3% to 4% total. So HBV is a very big problem in HIV-infected people.
When someone is infected with HIV, do the guidelines suggest that they also be tested for hepatitis B? Are HIV/HBV coinfected patients advised to get HBV treatment at the same time they're getting HAART?
The guideline recommendations are for HIV-positive individuals to be tested for hepatitis B at the time they're diagnosed with HIV. If they're not infected with hepatitis B, they should be vaccinated against it. If they are [infected with hepatitis B], then whether they should initiate treatment for both hepatitis B and HIV depends to some degree on how active their hepatitis B is and their stage of HIV infection, although most folks now are leaning more towards treating them earlier for both infections.
What's the take-home?
The take-home, I think, is that HAART is beneficial in regards to hepatitis B vaccine responses. Unfortunately, the responses we saw in individuals that were on HAART were still low: 44%.
How does that compare with HIV-uninfected people?
For non-infected individuals, it's about 90%, so there are a lot of factors that come into play. [HIV-infected individuals] need to make sure that they complete their vaccination series. That's another factor we found, which was very important.
HIV-infected people didn't complete their series?
Correct. In clinical practice, one limitation is that they may start the immunization series but don't complete it. That's been shown, in our study and in other studies. That's a very important point. They need to complete their vaccination series.
Could you talk a little bit about the patient characteristics here?
Sure. We had 626 individuals who had been vaccinated against hepatitis B. Overall, their median age was approximately 30 years. The breakdown of their ethnicity was about 45% Caucasian, [45%] African American and another 10% to 15% [representing] other ethnicities. CD4 cell counts at the time of their vaccinations were relatively preserved still, with a median of 490 cells. So, a relatively healthy group of patients.
Are these all veterans?
They are mostly folks serving on active duty or their dependents; they could also be veterans. But our cohort includes mostly active-duty individuals.
Most people don't know that HIV-infected individuals can still be on active duty.
HIV-infected individuals can continue to serve their country on active duty.
Were these people all located in Texas?
Our cohort is at seven participating Department of Defense military or medical treatment facilities, of which San Antonio, where I work, is one. The National Naval Medical Center in Bethesda [Md.] and Walter Reade here in Washington, D.C., are some other centers. Most folks are on active duty and followed in one of those clinics.
Was there any understanding of why people didn't continue with their vaccination series? Was it because they were being deployed to Iraq or elsewhere?
Great question. HIV-infected folks are not getting deployed, so they weren't going off to Iraq. But the next analysis we're planning is to look at factors that were associated with who at least started the series, and then who completed the series.
The military is an open-access care model, so that all health care, vaccines and medications are free of charge to the patient. There are pretty good guidelines for when you need to get staging evaluations for HIV while you're on active duty. We know that they are being seen in clinics, so the reasons why they're not completing their series aren't entirely clear.
We're going back all the way to 1988 here, so guidelines have changed over the years. Clinical practices have changed. Currently, our immunization coverage and completion rates are much better, but we haven't done the formal analysis of that.
In a military setting, isn't it easier to follow up with patients? They're all located within a small area.
That's right. It's what we call a closed health care system. So they do have to come to certain clinics to be seen.
This is a military world, but do we know what these people's risk factors were for HIV?
Now you're really starting to get out there and ask those probing questions. I can't tell you for our cohort overall. There was a study published a few years ago, looking at risk factors, but we don't have the data on everyone in the cohort.
Thank you very much.
This transcript has been lightly edited for clarity.