A single dose of measles vaccine does not provide 100% immunity in any case. Hence, the importance of >95% vaccination coverage for a community (not just geographic, but within an institution, such as a school or day care setting, sports club, household, religious or other community setting), including booster dosings. So I think the answer to the question is that it depends on the environment and that herd immunity is essential for child with SAM. In the context of an outbreak, quarantine of contacts who may be infectious is important (in addition to cohort isolation of symptomatic cases), and a child/children with SAM would reasonably require extra protection from exposure. Post-exposure prophylaxis for this population would also be priority consideration.

An additional point. Six to 59 months is a long interval. The immunity conferred by the initial vaccination wanes, so the time since last vaccination dose would also be relevant to answering the question posed.

Just to add to the very useful comments previously made, there isn't very good evidence that antibody responses to measles vaccine are worse in SAM, but some suggestion that the antibody responses may be delayed. See: http://jn.nutrition.org/content/139/11/2154S.long Overall, this adds to the argument that children with SAM may need additional protection from exposure.