Two or three doses of a vaccine against pneumococcal disease (pneumonia, meningitis or a blood stream infection) may be just as effective as the four-dose schedule currently recommended in the USA, according to a paper in this week's issue of The Lancet. The results are important because the four-dose schedule is expensive, and health-care providers and parents prefer that infants receive as few injections as possible. Also, in many part of the world routine infant immunisations can more easily accommodate a three-dose schedule.
When a pneumococcal vaccine against seven strains of Streptococcus pneumoniae was introduced in the USA, many children were vaccinated on schedules that differed from those tested in clinical trials. In this study researchers from the Centers for Disease Control and Prevention in the USA measured the effectiveness of the recommended dose schedule and incomplete schedules. 782 children, aged 3-59 months, with conditions that put them at risk of pneumococcal disease were enrolled into the study. Three healthy controls, matched for age and zip code, were selected for each case (2512 children). The investigators found that the vaccine was 96% effective against pneumococcal disease in healthy children who received one dose or more and 81% effective in children at risk of pneumococcal disease, such as those with chronic illnesses. They also found that compared with no vaccine the effectiveness of two, three and four-dose schedules were similar up to six months after vaccination (97% for two doses, 100% for three doses, and 100% for four doses). At 6 months or more months following vaccination, figures for effectiveness were still close (95% for two doses, 87% for three doses, and 100% for four doses).
The authors conclude: "The seven-valent pneumococcal conjugate vaccine prevents invasive disease in both healthy and chronically ill children. The vaccine is effective when used with various non-standard schedules…The next challenge is to ensure that conjugate vaccines become part of routine immunisation in more places, especially in developing countries where most pneumococcal deaths in young children occur."
Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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