Lower dose vaccine does the job

07 December 2008
Posted by Chris Smith.

When an epidemic looms, governments should stockpile vaccines.  That's a no brainer, but what if you have little warning, or the cost or development times are prohibitive?  Research in PloS Neglected Tropical Diseases suggests that a mere fraction of a vaccine may give enough short term immunity to stop an epidemic in it's tracks.

Line for meningitis vaccinations in Arua, Uganda
Line for meningitis vaccinations in Arua, Uganda © Sanjoy Ghosh

Looking at meningitis outbreaks in Sub-Saharan Africa, Phillipe Guerin and colleagues from institutions in Norway, Uganda and Manchester looked at the immune response of 750 healthy volunteers when they were given either a full dose of meningitis vaccine, one fifth of a dose or just one tenth.  They measured immune response by looking at something called serum bactericidal activity, which does exactly what it says on the tin - a measure of how effective a blood sample is at killing bacteria.  They took blood samples immediately before, then four weeks after vaccination, and tested them against 4 serotypes, subgroups of meningitis, called A, C, Y and W135.

So how did the partial doses fair against a full dose?  Well, of the 4 serotypes, a tenth dose of vaccine was as good as a full dose for types Y and W135.  One fifth of the vaccine dose was enough for group A, but only the full vaccine dose gave an adequate serum bactericidal activity for group C.

Clearly, we shouldn't be stretching our resources beyond our limits, but in times of emergency, controlling vaccine dose in this way could allow us to protect many more people in the time available, and could be what we need to stop an epidemic in it's tracks.

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