CTN 237: Influenza vaccination strategies using Fluviral in HIV-positive adults

About The Study

The objective of this study was to evaluate the immune response of three different seasonal influenza (Fluviral®) vaccine dosing strategies in HIV infected adults.

Researchers assessed which strategies worked best in producing an adequate immune response to the vaccine as measured by an antibody blood test.

Study Approach

Study participants were randomized into one of three groups:

• Group A: single standard dose injection of Fluviral
• Group B: standard dose injection of Fluviral followed 28 days later by a booster standard dose of Fluviral
• Group C: a double dose of Fluviral followed 28 days later by a second double dose of Fluviral.

All injections were given in the upper arm muscle. Groups A and B were compared to was Group C.

Study population

A total of 298 (90 per cent male, 98 percent on HAART) participants were recruited from 12 sites across Canada. Eligible participants were HIV-positive adults aged 18–60 years prior to the 2008–2009 influenza season. Of the enrolled participants, 84% had received the flu vaccine the previous year.

Results

Researchers measured serum hemagglutinin inhibition (HI) activity — the effectiveness of the vaccine to prevent influenza infection. Two hundred and ninety-seven participants received at least one injection. The primary outcome was a doubling of antibodies relative to baseline (start of study) at week 8, comparing groups A to C and B to C.

Over the 20-week period of assessment, 32 influenza-like illnesses (ILI) were reported, of these, six influenza infections were confirmed. ILI and positive infection results were evenly distributed between groups A, B and C. All dosing strategies were well tolerated. None of 8 serious adverse effects (SAEs) were immunization-related.

Conclusion

Double dose and booster dose Fluviral is well tolerated in HIV. Booster dosing or increased dosing may improve seroprotection in patients with low baseline SP levels to circulating influenza strains such as pandemic H1N1.