A bibliometric analysis of childhood immunization research productivity in Africa since the onset of the Expanded Program on Immunization in 1974

Table 4 Factors associated with childhood immunization research productivity identified by zero-truncated negative binomial regression models.

	Univariable		Multivariable
Variable	IRR (95% CI)	P-value	IRR (95% CI)	P-value
DTP3 coverage	0.38 (0.04, 3.42)	0.389	not included
Gross domestic product (US dollar)	1.46 (1.23, 1.73)	0.000	1.55 (0.82, 2.93)	0.177
Adult literacy rate	1.21 (0.36, 4.09)	0.764	not included
Physicians per 100,000 population	1.27 (0.92, 1.74)	0.147	0.77 (0.56, 1.04)	0.089
Total expenditure on health	3.98 (0.97, 16.21)	0.054	0.68 (0.12, 3.94)	0.665
Private expenditure on health	3.18 (1.62, 6.22)	0.001	3.64 (1.46, 9.07)	0.006
Research and development expenditure	1.47 (1.21, 1.78)	0.000	0.96 (0.49, 1.87)	0.897
Human development index	2.65 (0.45, 15.57)	0.280	not included

DTP3, third dose of the diphtheria-tetanus-pertussis vaccine by one year of age; IRR, incidence rate ratio; CI, confidence intervals