AIDSWEEKLY Plus, 24 June 1996
Daniel J. DeNoon, Senior Editor

A new finding casts doubt on the safety of influenza vaccination for HIV infected individuals.

Previous studies have detected a transient increase in the blood levels of people with HIV infection after influenza vaccination (e.g., D.D. Ho, Lancet, 1992;339:1549 and O'Brien et al., Blood, 1995;86:1082-9).

Nevertheless, current recommendations are for people with HIV infection to receive annual influenza immunizations.

Now a Norwegian research team has found that influenza immunization not only increases viral load but also increases the number of HIV infected cells.

Bard Rosok of the University of Bergen, Norway, and colleagues reported their findings in the journal Clinical and Experimental Immunology ("Dynamics of HIV-1 Replication Following Influenza Vaccination of HIV(+) Individuals," Clin Exp Immunol, 1996;104(2):203-207).

"Until further answers on harmful effects of vaccination are given, we suggest consideration of other methods of influenza prevention to avoid potential progression of HIV disease," they wrote.

Rosok et al. studied sequential blood samples from 10 HIV(+) individuals before and after influenza vaccination (a single intramuscular injection of 0.5 ml Fluzone 1994/95 split virus vaccine).

Nine of the 10 subjects had increased numbers of CD4 cells carrying infectious HIV provirus. In addition, four of six subjects with low viral loads had increased viral loads five days after vaccination.

"Current routine methods do not allow us to determine whether the observed increase in rate of infected cells in peripheral blood represents a real increase in the total number of virus-containing T cells, or whether it is due to redistribution of infected cells from lymphatic tissues," Rosok et al. noted.

However, until this issue can be resolved they suggested caution.

"The large increase in infected cells that we observe in patients with high viral load should be a cause of concern for the general recommendation to individuals in this patient group," Rosok et al. concluded. "The key question whether the observed increase in HIV load necessarily leads to a worsening of the HIV disease remains unanswered."

Financial support for this study was provided by Hoechst and Pasteurlegatet.

The corresponding author for this study is Bard Rosok, Centre for Research in Virology, Bergen High Technology Centre, University of Bergen, N-5020 Bergen, Norway.

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