3. Results
3.1. Vaccination compliance
Between 2016 to 2019 we followed the annual vaccination compliance among
566 cattle herd owners insured by ‘Hachaklait‘ (the veterinary
cooperation providing private veterinary services to the farmers). As
depicted in Figure 3, we observed a reduction in vaccination
against LSD from 61% in 2016 to 27% in 2019. We also found that
farmers who withdrew from vaccination were less likely to vaccinate in
the following years. Farmers who vaccinated their herd only in 2017 were
more than 8times more likely to vaccinate their herd in 2019 as compared
to the farmers who didn’t vaccinate their herd in 2017 and 2018. The
difference between farmers who didn’t vaccinate in both years to farmers
who vaccinate in both years was even more striking, where the latter was
120 times more likely to vaccinate in 2019 (Table 1 ). A strong
association was also found between vaccination and the geographical
location of the herd; farmers whose herd was located in the centre of
Israel were 20 times less likely, to vaccinate than farmers whose herd
was located in the north (Table 1 ).
3.2. Analysis of intention to vaccinate
To find the causes for this reduction in vaccination compliance we
distributed 90 questionnaires (Figure 1 ), based on the TPB
model, among Israeli dairy farmers (see detailed description in the
methods section). These questionnaires were analysed in a two-stage
approach. We first wished to characterize the factors determining the
farmers’ intention to vaccinate as a proxy for vaccination behaviour. At
the next stage, we aimed to explore which of these factors was both
likely to change with time and influence vaccination compliance.
Before the characterization of the factors influencing intention, we
wished to test the assumption that in our data the intention to
vaccinate represents vaccination behaviour. For this purpose, we used
the 56 questionnaires for which we had data on voluntary vaccination
(Figure 1, Data-intersect 1 ). As expected, analysis of these
questionnaires showed that vaccination among farmers who claimed they
are likely to vaccinate was 4.5 higher than among other farmers
(p-value=0.007). Analysis of 33 of these farmers for which we had data
on future behaviour showed a similar result though only marginally
significant (p=0.067). Surprisingly, despite this strong association,
only 19 out of the 38 (50%) farmers who claimed they are likely to
vaccinate indeed vaccinated their herd (Figure 1 ). The
vaccinating farmers showed a stronger belief in the ability of the
vaccine to reduce clinical signs of LSD (Table 2 ). However, the
most prominent difference between vaccinating and non-vaccinating
farmers was recorded in the indirect measurement of the PBC.
Specifically, these farmers were less concerned about the vaccine’s cost
and the time and manpower required for vaccination (Table 2 ).
We next analyzed the entire set of 90 questionnaires to identify the
factors that determine vaccination intention. Among the background
factors, farmers whose herds were located in the centre of Israel and
felt lower perceived risk regarding the frequency and consequences of an
LSD epidemic showed less intention to vaccinate their herds
(Table S2a,b ). Furthermore, as expected, higher vaccination
intention was associated with both direct and indirect measurements of
the three RAA constructs: attitude, subjective norms and perceived
behavioural control (Table S3 ). Among the attitude
factors, the highest influence was recorded for
the perceptions regarding the
benefit from vaccination, reduction of the severity of clinical signs,
receiving money from the insurance company, peace of mind and reducing
the number of disease cases. Farmers’ intention to vaccinate was
significantly influenced by all the nine investigated subjective norm
factors. Finally, among the PBC factors, the most influential were the
vaccine’s cost and information on the vaccine’s effectiveness
(Table S3 ).
At the following stage, we attempted to determine which of these factors
have changed as time elapsed from the LSD epidemic in 2012 and might
have caused the reduction in vaccination during 2016-2019. As explained
in the ‘Materials and Methods’, since we could not measure the actual
change of beliefs during this period we used the comparison between
farmers’ answers before and after the 2019 epidemic as a proxy for the
farmer’s change of beliefs shortly after the epidemic and long after an
epidemic.When comparing these two groups, we found that after the 2019
epidemic, the farmers showed higher intention to vaccinate
(Table 3). Furthermore, vaccination norms among farmers who
answered the questionnaires before the epidemic in 2019 were
significantly lower than the norms among farmers answering the
questionnaires after the epidemic (Table 3 ). Specifically,
after the epidemic the farmers perceived a stronger recommendation for
vaccination by the ’Hachaklait‘ and the veterinary services
(Table 3 ). In addition, after the epidemic, the farmers were
more concerned about the vaccine’s adverse reactions although the
overall attitude was not significantly different between the two groups
(Table 3 ). These findings suggest a possible connection between
a post epidemic change in these specific norms and a change in
vaccination intention.
The multivariable linear regression revealed four statistically
significant factors associated with farmers intention to vaccinate: the
time of questionnaire filling (higher for after the 2019 epidemic), the
farm location (lower in the centre of Israel) and two beliefs: The
farmer’s perceived recommendation to vaccinate by the private vet, and
the farmer belief that the vaccine will be economically worthwhile.
(Table 4 ).