A review of three decades of use of the cattle brucellosis rough vaccine Brucella abortus RB51: myths and facts

BMC Veterinary Research

Table 3 Controlled experiments in which RB51 protective efficacy (full dose) was evaluated in parallel with S19 (standard dose)^a

Experiment (reference)	Vaccine	Age at vaccination (months)	Nº bovines	Nº infected (%)	P vs Control^b	Relative Risk vs control (CI)^c	Attributable fraction (%)^d
6 [62, 71]^e	RB51	3–10	29	3 (10.3)	P < 0.01	5.8 (1.87–17.94)	82.7
	S19	3–10	22	1 (4.5)	P < 0.01	13.2 (1.88–92.6)	92.4
	Control	-	20	12 (60)
7 (SENASA data)^f	RB51	9	24	20 (83.3)	n.s.^g	1.2 (1.00–1.43)	16.6
	S19	9	29	18 (62)	P < 0.05	1.6 (1.21–2.14)	37.5
	Control	-	22	22 (100)
8 (NADC data)^h	RB51	3–10	87	20 (22)	P < 0.01	2.59 (1.65–4.06)	67.7
	S19	3–10	19	1 (5)	P < 0.01	11.31 (1.65–77.37)	91.9
	None	-	47	28 (60)		-	-
9 [130]ⁱ	RB51	16–18	10	5 (50)	P < 0.05	2 (1.07–3.71)	50.0
	S19	16–18	9	2 (22.2)	P < 0.01	4.5 (1.32–15.27)	77.7
	None	16–18	10	10 (100)

^aIn all experiments, a midgestational challenge was carried out and infection defined by bacteriological isolation of the challenge strain (B. abortus 2308 or B. abortus 544 in [130]). Bacteriological searches after challenge included at least milk, vaginal fluids, placenta and, after necropsy, mammary gland, spleen, liver and the most important lymph nodes. When described, bacteriological procedures are summarized in the footnote of each experiment
^bChi-square test
^cRelative Risk (RR) is the ratio of the probability of infection in the unvaccinated (control) and vaccinated groups; CI, confidence interval
^dPopulation attributable fraction (AF) estimates the proportion of infection cases that could be avoided by vaccination
^eChallenge administered conjunctively and, for bacteriological analyses, tissues were grinded and tenfold dilution inoculated in tryptone-broth and then plated on agar
^fThe SENASA (Servicio Nacional de Sanidad y Calidad Agroalimentaria, Argentina) data correspond to two experiments [131, 132]; the challenge was applied intramuscularly; bacteriology was performed on tryptone agar
^gn.s., not significant
^hOverall National Animal Disease Center (NADC) data on efficacy of brucellosis vaccines after experimental challenge (elaborated from [56])
ⁱTissue slices or homogenates plated on agar Brucella agar base plates

ISSN: 1746-6148