EMBARGOED-Partial vaccine dose may work as well as full shot

(Embargoed until 0100 Tues Dec 2)

LONDON, Dec 2 (Reuters) - Giving just one fifth the dose of a commonly used meningitis vaccine may be as effective as using the full dose, researchers said on Tuesday.

The finding should allow medics to stretch scarce vaccine resources, especially during epidemics in Africa.

A clinical study conducted in Uganda by Epicentre -- the research arm of medical charity Medecins Sans Frontieres -- found similar immune responses in patients given low and full doses of Sanofi-Aventis's vaccine Menomune.

Serum bactericidal activity (SBA) response with a one-fifth dose was comparable to full dose for three bacteria types targeted by the vaccine, though not a fourth.

Although another measure of immune response, IgG level, was lower for fractional doses, the researchers said short-term protection needed during mass vaccination programmes was best measured by SBA.

"In view of the current shortage of meningococcal vaccines for Africa, the use of one-fifth fractional doses should be considered as an alternative in mass vaccination campaigns," the research team reported in the journal PLoS Neglected Tropical Diseases.

Meningitis epidemics occur nearly every year across a large part of sub-Saharan Africa spanning Senegal to Ethiopia, dubbed the "Meningitis Belt".

Meningitis infects the lining of the brain and spinal cord and can cause high fever, blood poisoning and brain damage, as well as death in up to 10 percent of cases.

The full report on the study is available online at http://dx.plos.org/10.1371/journal.pntd.0000342 (Reporting by Ben Hirschler; Editing by Andrew Macdonald)