Conjugate vaccine prevents recurrent pneumococcal disease in HIV
In the New England Journal of Medicine for March 4, the investigators note that rates of pneumococcal infections are 30 to 100 times higher in patients with HIV than in the general population, and recurrence is common. However, the 23-valent pneumococcal polysaccharide vaccine has suboptimal activity in adults with HIV, is not recommended for use in Africa, and is best given early in the course of HIV infection.
On the other hand, studies have suggested that the 7-valent conjugate vaccine (Prevnar, Wyeth Pharmaceuticals) is more effective, but its potential for protection of HIV-infected adults has not been validated.
Lead author Dr. Neil French, from the London School of Hygiene and Tropical Medicine, Karonga, Malawi, and colleagues enrolled 496 survivors of invasive pneumococcal infection, ages 15 and older. "To avoid possible stigmatization of the study as an HIV trial, we offered enrollment to all patients...(recognizing) that the subgroup without HIV infection would be small," the authors write.
Indeed, 88.5% of participants had HIV infection. Overall, 93.8% of study subjects received two doses of Prevnar or placebo 4 weeks apart.
During a median follow-up of 1.2 years (798 person-years), 52 patients had 67 episodes of invasive pneumococcal disease, including 24 primary endpoint episodes, that is, disease due to vaccine serotypes or the 6A serotype. (The endpoint included 6A because reports have shown the vaccine affords cross-protection against this serotype.)
All endpoint episodes occurred in HIV-infected patients -- 5 in vaccine recipients and 19 in placebo recipients -- for an unadjusted vaccine efficacy of 74% in this population.
Efficacy was highest during the first year after vaccination.
Eighteen episodes (two in the vaccine group, 16 in the placebo group) occurred in patients with CD4 counts of less than 200 cells/mm3, translating to a vaccine efficacy of 86% in this subgroup.]
There was no significant difference between vaccine and placebo in the number of deaths from pneumococcal disease.
"It seems likely that the pneumococcal conjugate vaccine would also work as primary prophylaxis," Dr. French and colleagues suggest.
Malawi has started a national program for antiretroviral therapy, but the current trial was underpowered to detect an interaction between vaccine and anti-HIV drugs. The authors now call for research to study "whether a two-dose vaccine regimen...is optimal and how initial and repeat doses of vaccine should best be administered in relation to antiretroviral therapy to maximize the efficacy and duration of protection."
Wyeth Pharmaceutical provided the Prevnar vaccine for the intervention group during the trial and for the placebo group after the release of results.
N Engl J Med 2010;362:812-822.
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