Effectiveness of an outbreak dose of mumps-containing vaccine in two First Nations communities in Northern Ontario, Canada

Figures & data

Figure 1. Changes in recommended mumps vaccine schedule in Ontario, Canada.

Table 1. Population characteristics of Communities A and B at the start of the outbreak, crude attack rates, and unadjusted hazard ratios

Characteristics of the population prior to the outbreak		Cases* /Population	Crude Attack Rate (per 1000 persons)	Unadjusted Hazard Ratio (95% CI)	P-value
Overall		70/3135	22.3
Age group^†	<1 year	2/55	36.4	2.6 (0.5–9.3)	.23
	1 to <7 years	4/473	8.5	0.5 (0.2–1.6)	.28
	7 to <18 years	22/788	27.9	1.6 (0.7–3.7)	.26
	18 to <30 years	18/639	28.2	1.6 (0.8–3.9)	.22
	30 to <49 years	16/700	22.9	1.2 (0.5–2.9)	.69
	≥49 years	8/480	16.7	REF
Gender^‡	Male	47/1621	29.0	2.0 (1.2–3.5)	.005
	Female	23/1513	15.2	REF
Community	B	51/2129	24.0	1.0 (0.6–1.8)	.89
	A	19/1006	18.9	REF
Number of pre-outbreak dose(s) of vaccine received:	≥3 doses	0/54	0	0.8 (0.006–6.5)	.86
	2 doses	39/1445	27.0	2.3 (1.1–5.8)	.03
	1 dose	25/1086	23.0	1.9 (0.8–4.8)	.14
	0 doses	6/550	10.9	REF
Timing of pre-outbreak dose(s) of vaccine doses^§	Most recent dose: Received ≥20 years ago	32/962	33.3	2.7 (1.1–8.3)	.03
	Received ≥10 to <20 years ago	21/774	27.1	2.2 (0.9–7.1)	.10
	Received ≥3 to <10 years ago	7/478	14.6	1.3 (0.4–4.6)	.65
	Received <3 years ago	4/371	10.8	REF

*Confirmed and probable. ^†Age at the start of outbreak. ^‡Gender unknown for one individual.

^§Individuals who received no pre-outbreak doses of mumps-containing vaccine not shown.

Figure 2. [Panel A] Epi-curve for the 70 confirmed and probable cases of mumps occurring in Communities A and B: Dec 18, 2017, to June 27, 2018. [Panel B]: MMR vaccine doses administered in Communities A and B: Dec 18, 2017, to Jun 27, 2018.

Table 2. Unadjusted and adjusted hazard ratios for becoming a case of mumps among residents eligible to receive mumps vaccine (aged ≥1 year) during the outbreak, 18-Dec-2017 to 27-June-2018

		Penalized-likelihood Cox models
Variable		HR ^‡ estimate	95% Confidence Limits	P-value
Unadjusted estimates
Outbreak dose*	No outbreak dose	2.5	(0.9–9.4)	.08
	Receipt of outbreak dose	REF
Age group	1 to <7 years	0.5	(0.2–1.6)	.28
	7 to <18 years	1.6	(0.7–3.6)	.26
	18 to <30 years	1.6	(0.8–3.9)	.22
	30 to <49 years	1.2	(0.5–2.9)	.69
	≥49 years	REF
Gender	Male	2.1	(1.3–3.6)	.004
	Female	REF
Community	B	1.0	(0.6–1.8)	.99
	A	REF
Number of previous pre-outbreak dose(s) of vaccine	≥3 doses	1.0	(0.008–9.4)	1.0
	2 doses	3.0	(1.3–9.2)	.01
	1 dose	2.4	(1.0–7.7)	.06
	0 doses	REF
Timing of pre-outbreak dose(s) of vaccine^†	Most recent dose:
	Received ≥20 years ago	2.7	(1.1–8.3)	.03
	Received ≥10 to <20 years ago	2.2	(0.9–7.1)	.10
	Received ≥3 to <10 years ago	1.3	(0.4–4.6)	.65
	Received <3 years ago	REF
Adjusted estimates (multivariable model^§)
Outbreak dose *	No outbreak dose	2.7	(1.0–10.1)	.06
	Receipt of outbreak dose	REF
Age group	1 to <7 years	1.0	(0.2–5.4)	.97
	7 to <18 years	3.0	(1.0–9.3)	.05
	18 to <30 years	1.4	(0.6–3.5)	.44
	30 to <49 years	0.8	(0.3–2.0)	.57
	≥49 years	REF
Gender	Male	2.0	(1.2–3.5)	.006
	Female	REF
Timing of previous dose(s) of vaccine	No pre-outbreak vaccine	0.9	(0.2–4.8)	.91
	Most recent dose:
	Received ≥20 years ago	3.4	(0.7–20.6)	.13
	Received ≥10 to <20 years ago	1.4	(0.3–7.9)	.70
	Received ≥3 to <10 years ago	0.6	(0.2–4.8)	.61
	Received <3 years ago	REF

*Time-varying variable: the post-vaccine at-risk period begins 14 days following receipt of the outbreak dose.

^†Individuals who received no pre-outbreak doses of mumps-containing vaccine not shown.

^‡HR = Hazard ratio.

^§Multivariable model includes receipt of outbreak dose, age group, gender, and timing of previous dose(s) of vaccine.