Neethling vaccine proved highly effective in controlling lumpy skin disease epidemics in the Balkans

Abstract

Despite the wide use of the live attenuated Neethling lumpy skin disease (LSD) vaccine, only limited data existedon its efficacy and effectiveness prior to the large LSD epidemic in the Balkans, which took place during2016–2017. In addition, analysis of risk factors for the disease was hardly performed with proper control forvaccination effects and potential differences in exposure to the virus. Data from the LSD epidemics in six Balkancountries (Bulgaria, Greece, Serbia, Montenegro, Former Yugoslav Republic of Macedonia (FYROM) andAlbania) affected during 2016 were analyzed to determine vaccine effectiveness (VE) and risk factors for LSDinfection at the farm level. Vaccination was performed along the occurrence of the epidemics and thus vacci-nation status of some of the farms changed during the epidemic. To allow for this, left truncated and rightcensored survival analysis was used in a mixed effects Cox proportional hazard regression model to calculate VEand risk factors for LSD. The results indicated of an average VE of 79.8% (95% CI: 73.2–84.7)) in the sixcountries, with the lowest VE of 62.5% documented in Albania and up to VE of more than 97% as documented inBulgaria and Serbia. Analysis of time from vaccination to development of protective immunity showed that VEmostly developed during thefirst 14 days after vaccination. Data from Greece showed that the vaccinationadjusted hazard ratio for LSD was 5.7 higher in grazing farms compared to non-grazing farms. However, due to adifference in geographical location of grazing and non-grazing farms and higher vaccination rate in non-grazingfarms, this effect can be at least partly attributed to indirect protection due to herd immunity provided bysurrounding vaccinated farms.