The descriptive statistics of the key socio-economic characteristics of the sample for the multivariate regression indicate resonance with national statistics (Table 3).
Table 3: Summary statistics of the Study Sample
Variable
|
Obs
|
Mean
|
Std. Dev.
|
Min
|
Max
|
Age, years (Risk Severity risk 1)
|
4,440
|
40.47
|
15.04
|
18
|
90
|
Chronic illness (Risk Severity 2)
|
4,440
|
0.168
|
0.374
|
0
|
1
|
Well-informed (Barrier 1)
|
4,440
|
0.096
|
0.295
|
0
|
1
|
Household per capita income, Rands (Barrier 2)
|
4,440
|
2854
|
6135
|
0
|
150000
|
Education, years
|
4,440
|
11.52
|
3.729
|
0
|
22
|
African
|
4,440
|
0.782
|
0.413
|
0
|
1
|
Male
|
4,440
|
0.482
|
0.500
|
0
|
1
|
Married/with partner
|
4,440
|
0.479
|
0.500
|
0
|
1
|
Urban
|
4,440
|
0.760
|
0.427
|
0
|
1
|
Informal_dwelling
|
4,324
|
0.117
|
0.322
|
0
|
1
|
Electricity
|
4,440
|
0.946
|
0.226
|
0
|
1
|
Experienced Hunger
|
4,440
|
0.164
|
0.370
|
0
|
1
|
Employed
|
4,440
|
0.497
|
0.500
|
0
|
1
|
Social Grant recipient
|
4,440
|
0.353
|
0.478
|
0
|
1
|
Religious
|
4,440
|
0.913
|
0.282
|
0
|
1
|
Source: NIDS-CRAM weighted. # All variables except age, education and income are binary
The results of logit regressions highlight the role of risk and efficacy in driving vaccine hesitancy while controlling for other pertinent predictors (Table 4). Columns 1 - 3 and 4-6 are based on the HBM, and the EPPM respectively. Various specifications are estimated using log of per capital income, income quintiles and non-financial proxies for socio-economic status (hunger in household, household with electricity, grant recipient in household).
Table 4: Logit regression results: Dependent variable, Vaccine Hesitancy
|
(1)
|
(2)
|
(3)
|
(4)
|
(5)
|
(6)
|
VARIABLES
|
HBM
|
HBM
|
HBM
|
EPPM
|
EPPM
|
EPPM
|
Risk perception
|
-0.265**
|
-0.268**
|
-0.271**
|
|
|
|
|
(0.133)
|
(0.133)
|
(0.133)
|
|
|
|
Efficacy
|
-1.260***
|
-1.260***
|
-1.248***
|
|
|
|
|
(0.155)
|
(0.154)
|
(0.153)
|
|
|
|
Low risk^
|
|
|
|
0.429***
|
0.433***
|
0.429***
|
|
|
|
|
(0.125)
|
(0.124)
|
(0.124)
|
Denial^
|
|
|
|
1.061***
|
1.068***
|
1.052***
|
|
|
|
|
(0.230)
|
(0.230)
|
(0.231)
|
Severity 1(Age)
|
-0.0251***
|
-0.0260***
|
-0.0262***
|
-0.0216***
|
-0.0220***
|
-0.0221***
|
|
(0.00539)
|
(0.00531)
|
(0.00534)
|
(0.00472)
|
(0.00469)
|
(0.00469)
|
Severity 2 (chronic)
|
-0.155
|
-0.153
|
-0.158
|
-0.263*
|
-0.267*
|
-0.241
|
|
(0.175)
|
(0.175)
|
(0.176)
|
(0.155)
|
(0.155)
|
(0.156)
|
Barrier 1 (Information)
|
-0.287
|
-0.330
|
-0.338
|
-0.431**
|
-0.459**
|
-0.469**
|
|
(0.217)
|
(0.215)
|
(0.218)
|
(0.213)
|
(0.212)
|
(0.213)
|
Barrier 2 (education)
|
-0.0442**
|
-0.0511***
|
-0.0499***
|
-0.0370**
|
-0.0414**
|
-0.0437**
|
|
(0.0191)
|
(0.0196)
|
(0.0190)
|
(0.0177)
|
(0.0184)
|
(0.0176)
|
Barrier 3 (log PC HH Income)
|
-0.071*
|
|
|
-0.0694*
|
|
|
|
(0.0418)
|
|
|
(0.0389)
|
|
|
2. PC HH Income _Q2
|
|
0.036
|
|
|
0.068
|
|
|
|
(0.177)
|
|
|
(0.28)
|
|
3. PC HH Income _Q3
|
|
-0.348
|
|
|
-0.271
|
|
|
|
(0.223)
|
|
|
(0.194)
|
|
4. PC HH Income _Q4
|
|
-0.101
|
|
|
-0.0545
|
|
|
|
(0.201)
|
|
|
(0.178)
|
|
5. PC HH Income _Q5
|
|
0.0524
|
|
|
0.0118
|
|
|
|
(0.204)
|
|
|
(0.191)
|
|
Hunger
|
|
|
-0.216
|
|
|
-0.212
|
|
|
|
(0.167)
|
|
|
(0.149)
|
Electricity
|
|
|
0.135
|
|
|
-0.109
|
|
|
|
(0.302)
|
|
|
(0.259)
|
Grant receiving Household
|
|
|
0.210
|
0.136
|
0.144
|
0.154
|
|
|
|
(0.132)
|
(0.117)
|
(0.118)
|
(0.118)
|
African
|
-0.817***
|
-0.768***
|
-0.782***
|
-0.776***
|
-0.743***
|
-0.718***
|
|
(0.216)
|
(0.214)
|
(0.215)
|
(0.196)
|
(0.194)
|
(0.194)
|
NPI behaviour
|
-0.114**
|
-0.117**
|
-0.119**
|
-0.140***
|
-0.142***
|
-0.148***
|
|
(0.0578)
|
(0.0577)
|
(0.0577)
|
(0.0512)
|
(0.0513)
|
(0.0511)
|
male
|
-0.218*
|
-0.240*
|
-0.216*
|
-0.169
|
-0.182
|
-0.174
|
|
(0.125)
|
(0.126)
|
(0.124)
|
(0.114)
|
(0.115)
|
(0.113)
|
Married/Partnered
|
0.214
|
0.205
|
0.228*
|
0.251**
|
0.250**
|
0.237**
|
|
(0.132)
|
(0.131)
|
(0.133)
|
(0.120)
|
(0.119)
|
(0.120)
|
Employed
|
0.196
|
0.165
|
0.178
|
0.0406
|
0.0202
|
-0.0193
|
|
(0.130)
|
(0.133)
|
(0.131)
|
(0.121)
|
(0.122)
|
(0.120)
|
Religious
|
-0.0867
|
-0.0657
|
-0.0872
|
0.00923
|
0.0305
|
0.0226
|
|
(0.240)
|
(0.240)
|
(0.239)
|
(0.223)
|
(0.226)
|
(0.222)
|
Province controls
|
yes
|
yes
|
yes
|
yes
|
yes
|
yes
|
Constant
|
3.037***
|
2.529***
|
2.420***
|
1.544**
|
1.021*
|
1.235**
|
|
(0.635)
|
(0.579)
|
(0.676)
|
(0.601)
|
(0.556)
|
(0.613)
|
Wald chi2
|
138.57**
|
158.31***
|
158.14***
|
115.46***
|
122.23***
|
115.96***
|
Observations
|
4,264
|
4,264
|
4,235
|
4,441
|
4,441
|
4,440
|
Robust standard errors in parentheses, *** p<0.01, ** p<0.05, * p<0.1
^ the benchmark variable is Responsive (High risk-high efficacy)
The results of HBM specifications are consistent in underscoring the significance of risk perception of infection and efficacy as negative predictors of vaccine hesitancy. The EPPM results also indicate that individuals who perceive lower vulnerability to infection are more likely to be hesitant about accepting vaccine compared to the responsive (high risk and high efficacy) group.
The results indicate that, compared to responsive individuals, the low-risk individuals are more likely to be hesitant regarding the vaccine. We also see a significant difference between the vaccine intention of the ‘responsive’ and the ‘denial’ groups. This once again points to risk perception as being the driving factor, with no clear mediating role of efficacy being apparent.
Therefore, EPPM estimations further highlight the mediating role of efficacy, where the denial group (high risk-low efficacy) has a significantly higher vaccine hesitancy in relation to the responsive group. These results are insightful and suggest that it is important to accompany risk messaging with efficacy related communication to encourage individuals to accept vaccination.
Severity of risk, proxied through age has a significant negative association with vaccine hesitancy in both HBM and EPPM estimations. The second proxy for severity, chronic illness, is also significant in the EPPM model. The indication therefore is that in addition to vulnerability to infection, vaccine intentions are strongly driven by the perceived severity of risk as well.
Income, education and information availability are incorporated in the model as measures of barriers to adoption of health response. Education is likely to be correlated with both income and Covid related information, as such its significance is indicative of the key role that awareness plays in vaccine intentions. Similarly, the variable relating to information regarding COVID is negative (although significant only in the EPPM estimations) pointing to the need for creating more awareness and education around vaccines to reduce hesitancy. The income variable is rather weak and does not come out strong in the estimations. This however could be due to its strong correlation with some of the other variables in the model like education. The other proxies included to control for socio-economic status like experience of hunger, social grant receipt, and electrified dwelling also do not give any strong indications on their role in driving vaccine hesitancy. However, there is still the possibility that socio-economic status acts via risk perception and efficacy. This is explored further in section 10.
The positive association between adoption of NPI behaviour (measured as number of non-pharmaceutical preventive behaviour adopted) and vaccination is evident in both the HBM and EPPM models. There are other interesting socio-economic predictors of vaccine intention revealed through both HBM and EPPM estimations. Black Africans have significantly lower vaccine hesitancy compared to other race groups. Being married or having a partner is found to increase vaccine hesitancy significantly. This finding is contrary to expectations as being married is found in literature to have protective effect on health behaviour [46]. However, there have been studies [47] that cite negative relationship between vaccination and being married (or in a steady relationship). The result that males are on average less hesitant than females is consistent with the finding by [32] in the Australian context.
In order to remove any bias caused by the construct of the efficacy variable, we re-estimate the HBM and EPPM specifications excluding the observations where only vaccine hesitancy drives the efficacy variable. In other words, we drop observations where vaccine ineffectiveness takes the value one and the general efficacy variable is one. This ensures that there is no definitional relationship between the efficacy variable and the dependent variable of vaccine hesitancy. The results from this restricted estimation are given in appendix (table A1) and validates the results in Table 5.
As a further robustness check we also present results of ordinal logit regressions, where the dependent variable of vaccine intention is used in its original form with four response categories. The marginal effects of the regression relating to the key risk and efficacy variables for each of the four outcomes are presented in table 5.
The results are consistent with the logit regression with regards to risk and efficacy for the HBM model, and the risk-efficacy interaction variables (denial and low risk) for the EPPM model. The findings hold that risk perception, through the mediation of efficacy is driving vaccine intentions. The severity of risk proxied by age is significant predictor as in the logit model. There are however some deviations from the logit model in relation to chronic illness with it being significant in HBM but not in EPPM estimation. Education on the other hand, is significant only in the EPPM model for the ordinal estimation.
Table 5 Ordinal logit, marginal effects: Dependent variable, Vaccine Intention.
HBM
|
High Risk
|
High Efficacy
|
Severity-age
|
Severity-Chronic illness
|
Barrier-Education
|
Barrier-income
|
Barrier-information
|
Strongly accept vaccine
|
0.050**
|
0.197***
|
0.007***
|
0.070**
|
0.003
|
0.016
|
0.047
|
(0.024)
|
(0.031)
|
(0.001)
|
(0.032)
|
(0.003)
|
(0.011)
|
(0.045)
|
Somewhat accept vaccine
|
-0.012**
|
-0.048***
|
-0.002***
|
-0.017**
|
-0.001
|
-0.004
|
-0.011
|
(0.005)
|
(0.008)
|
(0.000)
|
(0.008)
|
(0.001)
|
(0.003)
|
(0.011)
|
Somewhat reject vaccine
|
-0.009**
|
-0.038***
|
-0.001***
|
-0.014**
|
-0.001
|
-0.003
|
-0.010
|
(0.004)
|
(0.009)
|
(0.000)
|
(0.006)
|
(0.001)
|
(0.002)
|
(0.009)
|
Strongly reject vaccine
|
-0.028**
|
-0.111***
|
-0.004***
|
-0.039**
|
-0.002
|
-0.009
|
-0.026
|
(0.016)
|
(0.024)
|
(0.001)
|
(0.020)
|
(0.002)
|
(0.006)
|
(0.025)
|
EPPM
|
Denial ^
|
Low risk^
|
Severity-age
|
Severity-Chronic illness
|
Barrier-Education
|
Barrier-income
|
Barrier-information
|
Strongly accept vaccine
|
-0.173***
|
-0.066***
|
0.007***
|
0.055
|
0.008**
|
0.016
|
0.039
|
(0.044)
|
(0.024)
|
(0.001)
|
(0.036)
|
(0.002)
|
(0.011)
|
(0.044)
|
Somewhat accept vaccine
|
0.040***
|
0.016***
|
-0.002***
|
-0.013
|
-0.002**
|
-0.004
|
-0.010
|
(0.011)
|
(0.005)
|
(0.000)
|
(0.009)
|
(0.000)
|
(0.003)
|
(0.011)
|
Somewhat reject vaccine
|
0.035***
|
0.013***
|
-0.002***
|
-0.012
|
-0.002**
|
-0.003
|
-0.008
|
(0.003)
|
(0.006)
|
(0.000)
|
(0.008)
|
(0.000)
|
(0.002)
|
(0.009)
|
Strongly reject vaccine
|
0.037***
|
0.098***
|
-0.004***
|
-0.030
|
-0.005**
|
-0.009
|
-0.022
|
(0.018)
|
(0.025)
|
(0.001)
|
(0.020)
|
(0.000)
|
(0.006)
|
(0.024)
|
Robust standard errors in parentheses, *** p<0.01, ** p<0.05, * p<0.1, ^Benchmark category is responsive (high risk-high efficacy)