Measles immunization strategies for countries with high transmission rates: interim guidelines predicted using a mathematical model.

This study addresses the problem of measles immunization in communities experiencing unacceptably high numbers of cases in young infants, under circumstances where high dose Edmonston-Zagreb vaccine is not yet available. Where the continued use of standard potency vaccines (eg Schwarz) is unavoidable we have investigated the merits of new policies which aim to offer better protection to children below the currently recommended vaccination age of nine months. These policies are intended for implementation in communities with intense measles transmission. Predictions, spanning five years, using a previously developed mathematical model are presented for two types of potential new policies: a 'switch' to a younger target age, or a 'two-dose' strategy incorporating vaccination at a younger age in addition to the current schedule at nine months. We conclude that a switch in immunization policy to a younger age is of doubtful worth, but that supplementary vaccination at around six months in addition to existing coverage at nine months (ie two-dose policy) is a desirable option.