Foot-and-mouth disease (FMD) in Turkey is controlled using six-monthly mass vaccination of cattle. However, vaccine protection is undermined by population turnover and declining immunity. We assessed population immunity using a dynamic model of the cattle population in Anatolian Turkey in 2012/13, assuming biannual mass vaccination with a single-dose primary course. Six months after the last round of vaccination almost half the cattle aged <24 months remain unvaccinated. Five months after the last roundof vaccination two-thirds of cattle would have low antibody titres (<70% protection threshold). Giving a two-dose primary vaccination course reduces the proportion of 6-12 month old cattle with low titres by 20-30%. Biannual mass vaccination of cattle leaves significant immunity gaps. Improved vaccines are now used. However, without effective movement restrictions and biosecurity, the extent to which FMD can be controlled by vaccination alone remains uncertain.
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