Assessment of effectiveness of a foot-and-mouth
disease vaccine in cattle in Ethiopia
Wudu T. Jemberu1,2, Wassie Molla2, Tsegaw Fentie2and Theodore Knight-Jones1
1International Livestock Research Institute, Ethiopia
2University of Gondar
22nd International Symposium of Veterinary Epidemiology and Economics
Halifax, Canada, 12 August 2022

Introduction
• Foot and mouth disease (FMD) causes
global impact and is endemic in many
developing countries in Africa and Asia
• In endemic situations, vaccination is
widely used to control the disease and
is the main tool in the global FMD
control strategy
WOAH Official status FMD (WOAH, 2021)

• A quality effective vaccine is a critical requirement for successful control of animal
diseases through immunization and has been a problem for some FMD vaccination
programmes
• FMD is endemic in Ethiopia and there is an increasing trend of using FMD vaccine
to contain FMD outbreaks
• Most of the vaccines currently used in Ethiopia are produced within the country
• The effectiveness of these vaccines under field conditions has not been evaluated
Objective
• Evaluate the field effectiveness of the FMD vaccine currently produced and used in
Ethiopia in terms of preventing clinical infection and severe disease in cattle
Introduction

Materials and Methods
Study area
• Gondar Zuria district, North Gondar administrative
zone, Northwest Ethiopia
• Traditional mixed crop-livestock production system
• No history of FMD in the preceding fours years
• FMD vaccination never previously practiced
• An outbreak of FMD occurred in two villages of the
district (Maksegnet and Enfranze areas) 2017/18
• Cattle herds in 32 villages adjacent to the outbreak
area where the outbreak was anticipated to spread were
used for the study

Study design:
Randomized controlled effectiveness trial
20 days
post
vaccination
Epi unit (site)= #2
Infected village= #2
Free but at-risk village= #32
Household herds = #468
Unvaccinated cattle = #2867
Vaccinated Cattle = #3780
Infected Cattle
At risk village
Herd in village-
vaccinate 50%
Farmer records which
cattle develop FMD

• The outbreak spread during the follow up period
Materials and Methods.
Study sites No. of
initially free
villages
No. of herds
involved in the
vaccination trial
No. of villages
where OB
spread
No. of
vaccinated herds
in OB villages
No of vaccinated herds
from which effectiveness
data was collected
Makesegnet area 25 646 15 430 342
Enfranze area 7 346 1 38 33
Total 32 992 16 468 375

• The outbreak spread during the follow up period
Materials and Methods.
Study sites No. of
initially free
villages
No. of herds
involved in the
vaccination trial
No. of villages
where OB
spread
No. of
vaccinated herds
in OB villages
No of vaccinated herds
from which effectiveness
data was collected
Makesegnet area 25 646 15 430 342
Enfranze area 7 346 1 38 33
Total 32 992 16 468 375

• The outbreak spread during the follow up period
Materials and Methods.
Study sites No. of
initially free
villages
No. of herds
involved in the
vaccination trial
No. of villages
where OB
spread
No. of
vaccinated herds
in OB villages
No of vaccinated herds
from which effectiveness
data was collected
Makesegnet area 25 646 15 430 342
Enfranze area 7 346 1 38 33
Total 32 992 16 468 375

• The vaccine was an inactivated trivalent vaccine containing O, A, and SAT2 serotypes with
saponin adjuvant produced in Ethiopia with 3PD50 potency
• Administered once for cattle > 6 months old
• Outbreaks were confirmed to be caused by FMDV serotype O, topo type EA-3
• Follow up for clinical cases was done through farmer reporting and clinical confirmation by the
investigators
• Clinical cases were recorded as mild or severe
• No blinding or placebo were employed
Materials and Methods

Vaccine effectiveness
“Percentage reduction in incidence in vaccinated compared to unvaccinated individuals in the field”
𝑉𝐸 = 1 − 𝑅𝑅
Materials and Methods

Effectiveness against clinical disease
Vaccine effectiveness 20 days post vaccination
Results
Herds and vaccination
status
Number of cattle
monitored
(185 herds)
No. of clinically
affected cattle
Attack rate
(%)
Vaccine
effectiveness
(%) (95%CI)
Vaccinated 660 224 34%
31% (20-40)
Unvaccinated 490 240 49%
Total 1150 464 40%
P value < 001 Relative risk = 0.69

Vaccination status Number of cattle
monitored
(185 herds)
Number of
clinically
affected cattle
Attack rate (%) Vaccine
effectiveness
(%) (95%CI)
Vaccinated 486 50 10%
52% (33-66)
Unvaccinated 318 68 21%
Total 804 118 15 %
Results
Effectiveness against clinical disease
Vaccine effectiveness 42 days post vaccination
P-value < 0.001 Relative risk = 0. 48

Effectiveness against SEVERE clinical disease
Vaccine effectiveness 20 days post vaccination
Results
Vaccination
status
Number of cattle
monitored
(185 herds)
Number of
clinically
affected cattle
Attack rate (%) Vaccine
effectiveness
(%) (95%CI)
Vaccinated 1257 72 5.7%
39% (18-55)
Unvaccinated 930 87 9.4%
Total 2187 159 7.3%
P value <0. 001 Relative risk = 0.41

• The evaluated vaccine has lower effectiveness (31-52%) in cattle than >75%
recommended percentage of protection for 3PD50 vaccines (WOAH, 2018)
• If FMD R0 is 1.68 (Tadesse et al., 2019) [a low estimate] then >40% must be
immune to achieve herd immunity – will the vaccine achieve this if high is
coverage?
• The vaccine was better at preventing severe disease
• Improvement in vaccine effectiveness required regardless
• Based on reduction in disease burden it may pay to vaccinate even if herd
immunity is not achieved, especially given low vaccine price
• US$0.4/dose – 100 cattle=US$40
• to be confirmed with further analysis
Conclusions

Thank you for your attention
Comments and Questions?

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