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Invasive Streptococcus pneumoniae infections remain a threat to HIV-infected individuals, particularly in sub-Saharan Africa. Because unconjugated pneumococcal vaccine provides suboptimal protection for HIV-infected adults and is not recommended for use in Africa, new approaches for preventing pneumococcal disease in this population are needed.
In a recent double-blind, randomized, placebo-controlled trial conducted in Malawi, researchers evaluated the efficacy of a 7-valent pneumococcal conjugate vaccine in patients aged ≥15 years who were recovering from documented invasive pneumococcal disease (IPD). Of 977 eligible patients, 496 were enrolled, of whom 88.5% were HIV seropositive. A total of 273 patients were included in the follow-up analysis (median duration of follow-up, 1.2 years).
Sixty-seven episodes of IPD occurred in 52 patients, all of whom were HIV infected. Vaccine efficacy was 74% (95% confidence interval, 30%–90%). Serious adverse events were more common in the placebo group than in the vaccine group (17 vs. 3; P=0.002). A nonsignificant excess of deaths was seen in the vaccine group (hazard ratio, 1.18; 95% CI, 0.84–1.66).
French N et al. A trial of a 7-valent pneumococcal conjugate vaccine in HIV-infected adults. N Engl J Med 2010 Mar 4; 362:812.
Comment
The “pediatric” vaccine prevented recurrent IPD episodes in this cohort of HIV-infected adolescents and adults, most of whom were HIV infected. The lack of survival benefit among vaccine recipients was unanticipated. Might the preenrollment IPD episode have induced a level of immune protection sufficient to prevent death, but not recurrent infection? The higher rate of serious adverse events in the placebo group was also unexpected. Further evaluation of these events, however, revealed that many of them might have been caused by undiagnosed pneumococcal infection.