Protective effects of high-potency FMDV O 1 Manisa monovalent vaccine in cattle challenged with FMDV O/SKR/2010 at 7 or 4 days post vaccination

Emergency Foot-and-Mouth Disease Vaccines A Malaysia 97 and A22 Iraq 64 Offer Good Protection against Heterologous Challenge with A Variant Serotype A ASIA/G-IX/SEA-97 Lineage Virus

“…The vaccines conferred partial protection in 60%-80% of the calves by 7 dpv, and 100% protection in those challenged on 21 dpv. The time interval between the vaccinations and infection is unpredictable in an outbreak, and this study confirms previous reports that the number of days between vaccination and infection significantly influences the outcome whilst emergency vaccines with a higher antigen content can be effective despite a poor antigenic match [17,22,[31][32][33][34]. It has also been suggested that vaccination reduces transmission (reproduction ratio below 1; R 0 < 1), even if animals become infected, mainly by reduction of infectivity, which is probably correlated with the reduction of clinical disease and excretion [35].…”

“…The heterologous neutralizing antibody titers to the challenge virus were lower than the homologous titers in most of the animals, but apparently enough to offer clinical protection in all but three calves, despite the severe direct challenge by IDL route. Under field conditions, it is likely that exposure to FMDV will be less severe and therefore it can be expected that the clinical protection would be better than what was observed in this study [34]. During a response to an outbreak, when movement restrictions will be enforced, exposure will be further mitigated.…”

“…Several studies showed that reduction of transmission can be achieved within 14 days after vaccination [35][36][37][38][39]. There are strong indications that virus excretion is reduced when a challenge occurs even earlier post-vaccination [34,40,41]. Therefore, in case of an FMD incursion, an early decision for emergency vaccination is necessary to allow enough opportunity for a mature immune response and better protection [32,34].…”

Cross-Protection Induced by a A/MAY/97 Emergency Vaccine Against Intra-Serotype Heterologous Challenge with a Foot-and-Mouth Disease Virus from the A/ASIA/G-VII Lineage

“…The formula above shows that under the assumption that one should have at least 3 PD 50 /dose against the heterologous field virus; the cross-protection-ratio (and probably the r 1 -value) should not be below 0.5. However, the homologous potency of emergency vaccines is often much larger than 6 PD 50 /dose [6][7][8][9]22]. Therefore, managers of vaccine banks should not require vaccine of >6 PD 50 /dose but should know the homologous potency to be able to predict the protection against circulating field viruses, using in-vitro vaccine matching results (e.g., r 1 -value) as predictor of the cross-protection-ratio.…”

“…These low r 1 -values (below 0.3) are generally considered indicative of a low antigenic match between the vaccine strain and field isolate, which may result in poor protection. However, emergency vaccines formulated with high antigen content from vaccine bank antigens often perform better than the results predicted from the in vitro vaccine matching test, and emergency vaccines with vaccine strains that have a relatively low r 1 -values against a field strain can provide sufficient intra-serotype heterologous protection [6][7][8][9]. In order to determine intra-serotype heterologous protection against G-VII, Waters et al [5] performed an in vivo study to assess the level of protection provided by a single dose of a routinely used multi-valent vaccine containing A/IRN/05 and A/SAU/95 (as well as 3 serotype O antigens; O Manisa, O 3039, O PanAsia-2, and 1 serotype Asia1 antigen as well as 1 serotype SAT2 antigen).…”