Whatever Happened to H1N1 (Swine Flu) and HIV? New Answers at CROI 2010

The H1N1 pandemic that swept the world in 2009 caused plenty of panic and media hype. But given the small amount of available data on H1N1 at the time, HIV care providers were left with more questions than answers, including whether H1N1 acquisition risk was higher for HIV-infected people, whether H1N1 infection was more severe in HIV-infected people, and whether the H1N1 vaccine would be as effective in HIV-infected patients as in HIV-uninfected patients. A series of posters presented here at CROI 2010 answers some of those questions.

There were three key take-away messages from the posters:

1. H1N1 was not worse in, and did not worsen, HIV. In HIV-infected people with well-managed conditions (good CD4+ cell counts, low viral loads), H1N1 was not more severe than it was in the general population, according to the research presented by Esteban Martinez of Hospital Clínic de Barcelona. In addition, H1N1 did not appear to have any negative impact on the CD4+ cell counts or viral loads of HIV-infected patients. People with advanced HIV disease, however, did appear to face a higher risk for experiencing potentially life-threatening complications from H1N1 infection.

2. Don't confuse H1N1 with an opportunistic infection. HIV-infected patients who had opportunistic respiratory infections and were infected with H1N1 often got diagnosed and treated for the opportunistic infection, but not the H1N1, leading to complications and even death, according to research presented by Gustavo Reyes-Terán of Instituto Nacional de Enfermedades Respiratorias in Mexico City. His team determined that in 25% of cases, the symptoms of the opportunistic infection were masking the H1N1 symptoms. Reyes-Terán recommended that any HIV-infected patient who presents with respiratory illness should either be tested for H1N1 (if a rapid test is available) or treated empirically for the flu.

3. For people with HIV, two H1N1 vaccine doses may be better than one. Markus Bickel of Goethe University Hospital in Frankfurt, Germany, presented a study revealing that the inactivated, adjuvanted H1N1 vaccine did not work as well in HIV-infected populations when administered as a single dose. (It was about 69% successful in his study, compared to 79% and upward for the general population.)

Bickel added, however, that there appeared to be signs that when the H1N1 vaccine was administered in two doses (as was originally intended; subsequent studies in the general population suggested one dose was enough), the vaccine worked just as well for HIV-infected populations as the single dose worked in the general population. This data was not processed in time to be included in his poster presentation at CROI, Bickel said. He urged more study to confirm the findings.

In general, the HIV-infected population has never fared as well as the general population with influenza vaccines. But the difference in rates of failure with a single dose of H1N1 vaccine when comparing HIV-infected patients to the general population was much greater than it normally is with the seasonal flu vaccine.

Based on the findings of his study, Bickel suggested that HIV-infected people needed to be considered, and researched, as a separate group from the general population when studying vaccinations in the future.