FluWatch report: March 22 to 28, 2020 (week 13)

Influenza/Influenza-like Illness (ILI) Activity (geographic spread)

During week 13, influenza activity was reported in 33 regions across Canada and 4 regions reported no influenza activity. Among the regions reporting influenza activity, 65% reported sporadic activity and 24 % reported localized activity (Figure 1).

Figure 1 - Text equivalent

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	No Data
N.L.	Labrador-Grenfell	Sporadic
N.L.	Central	No Data
N.L.	Western	Sporadic
P.E.I.	Prince Edward Island	Sporadic
N.S.	Zone 1 - Western	Sporadic
N.S.	Zone 2 - Northern	Sporadic
N.S.	Zone 3 - Eastern	Sporadic
N.S.	Zone 4 - Central	Sporadic
N.B.	Region 1	Localized
N.B.	Region 2	Sporadic
N.B.	Region 3	Sporadic
N.B.	Region 4	No Activity
N.B.	Region 5	Sporadic
N.B.	Region 6	Localized
N.B.	Region 7	Localized
Que.	Nord-est	Sporadic
Que.	Québec et Chaudieres-Appalaches	No Activity
Que.	Centre-du-Québec	Localized
Que.	Montréal et Laval	Sporadic
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	No Activity
Ont.	Central East	Localized
Ont.	Central West	Localized
Ont.	Eastern	Localized
Ont.	North East	Localized
Ont.	North West	Sporadic
Ont.	South West	Localized
Ont.	Toronto	No Data
Man.	Northern Regional	No Data
Man.	Prairie Mountain	No Data
Man.	Interlake-Eastern	No Data
Man.	Winnipeg	No Data
Man.	Southern Health	No Data
Sask.	North	No Data
Sask.	Central	No Data
Sask.	South	No Data
Alta.	North Zone	No Data
Alta.	Edmonton	No Data
Alta.	Central Zone	No Data
Alta.	Calgary	No Data
Alta.	South Zone	No Data
B.C.	Interior	Sporadic
B.C.	Fraser	Sporadic
B.C.	Vancouver Coastal	Sporadic
B.C.	Vancouver Island	Sporadic
B.C.	Northern	Sporadic
Y.T.	Yukon	Sporadic
N.W.T.	North	Sporadic
N.W.T.	South	Sporadic
Nvt.	Qikiqtaaluk	Sporadic
Nvt.	Kivalliq	No Activity
Nvt.	Kitimeot	Sporadic

Laboratory-Confirmed Influenza Detections

In week 13, the percentage of laboratory tests positive for influenza continued to decrease sharply to 2.5%. The percentage of positive tests crossed the seasonal threshold of 5%, suggesting that the end of the influenza season at the national level may have occurred last week.

Testing for influenza and other respiratory viruses may be influenced by the current COVID-19 pandemic. Changes in laboratory testing practices in the coming weeks may affect the comparability of data to previous weeks or previous seasons.

The following results were reported from sentinel laboratories across Canada (Figures 2 and 3):

• 50% of detections were influenza A.
• Among subtyped influenza A detections, influenza A(H1N1) accounted for 66% of detections.

To date this season (weeks 35 to 13), all influenza types and subtypes have circulated. Among the 55,033 laboratory detections of influenza reported:

• 59% (32,547) were influenza A.
• Among subtyped influenza A detections (7,288), A(H1N1) is the predominant subtype this season (68%).

Detailed information on age and type/subtype has been received for 42,355 laboratory-confirmed influenza cases (Table 1). To date this season (weeks 35 to 13):

• Cases of influenza A(H1N1) (3,729) were primarily in adults; 26% 20-44 years, 26% 45-64 years and 28% 65 years of age and older.
• Among cases of influenza A(H3N2) (2,048), the largest proportion of cases was in adults 65 years of age and older (46%).
• Cases of influenza B (18,086) were primarily in younger age groups; 22% under 5 years of age, 33% 5-19 years and 31% between 20 and 44 years of age.

For more detailed weekly and cumulative influenza data, see the text descriptions for Figures 2 and 3 or the Respiratory Virus Detections in Canada Report.

Number of Laboratories Reporting in Week 13: 33 out of 36

The shaded area indicates weeks where the positivity rate was at least 5% and a minimum of 15 positive tests were observed, signalling the period of seasonal influenza activity.

Figure 2 - Text equivalent

Surveillance Week	A(Unsubtyped)	A(H3N2)	A(H1N1)	Influenza B	Percent Positive A	Percent Positive B
35	10	16	0	2	1.3	0.1
36	11	13	2	2	1.1	0.1
37	5	17	2	5	0.9	0.2
38	11	15	3	6	1.0	0.2
39	11	21	2	3	1.0	0.1
40	34	9	1	2	1.2	0.1
41	34	18	0	5	1.4	0.1
42	54	12	1	14	1.6	0.3
43	44	13	7	17	1.6	0.3
44	43	23	16	17	1.8	0.3
45	57	57	20	39	2.2	0.7
46	82	43	23	77	2.7	1.4
47	118	49	33	124	3.1	1.9
48	225	67	42	223	4.9	3.2
49	281	79	41	336	5.3	4.1
50	463	100	73	654	7.7	8.0
51	794	149	169	1094	10.6	10.4
52	1223	267	197	1439	15.0	12.7
1	1620	261	431	1533	15.8	10.3
2	1690	165	493	1463	15.8	9.4
3	1575	139	417	1418	16.2	10.3
4	1727	133	370	1952	15.2	12.7
5	1983	97	440	2269	16.0	13.7
6	1970	75	344	2265	15.6	14.1
7	1741	76	321	1851	15.5	12.8
8	1768	74	255	1559	16.3	11.6
9	1928	58	303	1287	16.7	8.9
10	1773	81	399	1152	13.6	6.5
11	1552	70	354	1016	9.8	4.3
12	830	38	152	594	4.8	2.5
13	179	17	33	265	1.3	1.3

Figure 3 - Text equivalent

ProvincesTable Figure 3 - Footnote 1	Cumulative (August 25, 2019 to March 28, 2020)
	A Total	A(H1N1)	A(H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	A & B Total
B.C.	4072	276	243	1846	2552	6624
Alta.	4352	1721	1285	1346	3403	7755
Sask.	1370	59	102	1209	700	2070
Man.	1637	174	134	1329	883	2520
Ont.	6468	2563	459	3446	2554	9022
Que.	12827	0	0	12827	10025	22852
N.B.	1045	60	29	956	1292	2337
N.S.	195	3	2	190	238	433
P.E.I.	144	0	0	144	78	222
N.L.	200	8	33	159	491	691
Y.T.	70	4	8	55	35	105
N.W.T	107	87	19	1	186	293
Nvt.	60	5	14	41	49	109
Canada	32547	4960	2328	23549	22486	55033
PercentageTable Figure 3 - Footnote 2	59%	15%	7%	72%	41%	100%
Table Figure 3 - Footnote 1 Specimens from NWT, YT, and Nvt are sent to reference laboratories in other provinces. Return to Table Figure 3 - Footnote 1 referrer Table Figure 3 - Footnote 2 Percentage of tests positive for sub-types of influenza A are a percentage of all influenza A detections. Return to Table Figure 3 - Footnote 2 referrer Table Figure 3 - Footnote 3 Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Return to Table Figure 3 - Footnote 3 referrer

Table 1 - Cumulative number of positive influenza specimens by type, subtype and age group reported through case-based laboratory reporting, Canada, weeks 2019-35 to 2020-13

Age groups (years)	Cumulative (August 25, 2019 to March 28, 2020)
	Influenza A				B	Influenza A and B
	A Total	A(H1N1)	A(H3N2)	A (Un subtyped) Table 1 Footnote 1	Total	#	%
0-4	3797	441	213	3143	4037	7834	18%
5-19	2741	297	261	2183	5983	8724	21%
20-44	5216	963	330	3923	5539	10755	25%
45-64	5012	978	303	3731	1143	6155	15%
65+	7503	1050	941	5512	1384	8887	21%
Total	24269	3729	2048	18492	18086	42355	100%
Table 1 Footnote 1 Unsubtyped: The specimen was typed as influenza A, but no result for subtyping was available. Table 1 Return to footnote 1 referrer

Syndromic / Influenza-like Illness Surveillance

Healthcare Professionals Sentinel Syndromic Surveillance

In week 13, 1.1% of visits to healthcare professionals were due to influenza-like illness (ILI) which is a slight decrease from the previous week and around average for this time of year (Figure 4). This trend should be interpreted with caution as there continues to be a decreasing number of sentinels reporting. Given the evolving Canadian situation with COVID-19, we will continue to monitor this indicator closely.

Number of Sentinels Reporting in week 13: 60

The shaded area represents the maximum and minimum percentage of visits for ILI reported by week from seasons 2014-2015 to 2018-2019

Figure 4 - Text equivalent

Surveillance Week	2019-2020	Average	Min	Max
35	0.6%	0.6%	0.4%	0.9%
36	0.4%	0.6%	0.4%	0.9%
37	0.7%	0.7%	0.5%	1.0%
38	1.1%	0.7%	0.6%	1.0%
39	0.8%	0.9%	0.5%	1.2%
40	1.0%	1.2%	0.8%	1.7%
41	0.9%	1.7%	0.8%	2.8%
42	1.1%	1.6%	1.2%	2.1%
43	0.7%	1.2%	0.8%	1.7%
44	0.9%	1.2%	0.7%	1.7%
45	0.7%	1.2%	0.9%	1.5%
46	1.1%	1.4%	1.2%	1.8%
47	1.2%	1.6%	1.1%	2.2%
48	0.9%	1.5%	1.1%	2.2%
49	1.0%	1.7%	1.0%	2.8%
50	1.4%	1.5%	1.1%	1.7%
51	1.1%	1.9%	1.4%	2.7%
52	2.5%	2.0%	1.0%	3.1%
1	2.9%	3.4%	1.9%	5.4%
2	1.5%	3.4%	1.8%	5.7%
3	1.8%	2.3%	1.3%	3.7%
4	1.4%	2.0%	1.1%	2.9%
5	1.5%	2.1%	1.4%	3.1%
6	1.7%	2.4%	1.4%	4.0%
7	1.3%	2.4%	0.9%	3.5%
8	1.4%	2.3%	0.8%	3.4%
9	1.4%	2.3%	0.9%	3.1%
10	1.4%	2.0%	1.0%	2.8%
11	1.7%	1.9%	1.1%	2.8%
12	1.4%	1.6%	0.6%	2.6%
13	1.1%	1.6%	1.1%	2.6%

FluWatchers

In week 13, 3,124 participants reported to FluWatchers, of which 0.9% (27) reported symptoms of cough and fever (Figure 5).The percentage of participants reporting cough and fever continue to decrease and are at the lowest levels ever observed. This may be due to social distancing measures implemented in recent weeks. Given the evolving Canadian situation with COVID-19, we will continue to monitor this indicator closely.

Among the 27 participants who reported cough and fever:

• 38% consulted a healthcare professional, a larger proportion than in recent weeks;
• 52% reported days missed from work or school, a similar proportion to the previous week, resulting in a combined total of 56 missed days of work or school.

If you are interested in becoming a FluWatcher, sign up today.

Number of participants reporting in week 13: 3,124

Figure 5 - Text equivalent

Surveillance Week	% cough and fever
40	2.2%
41	1.8%
42	1.7%
43	2.2%
44	1.6%
45	1.4%
46	1.2%
47	1.5%
48	1.7%
49	2.2%
50	2.1%
51	2.6%
52	4.1%
1	4.3%
2	3.1%
3	3.3%
4	3.1%
5	3.4%
6	3.0%
7	2.7%
8	2.7%
9	2.4%
10	2.1%
11	2.5%
12	1.5%
13	0.9%

Online Figure - Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2020-13

Click on the map to access the link

Influenza Outbreak Surveillance

In week 13, a total of 5 outbreaks were reported: 3 in long term care facilities and 2 in acute care facilities (Figure 6).

To date this season, a total of 903 laboratory-confirmed influenza outbreaks have been reported; 65% (583) in long-term care facilities, 25% (221) in facilities categorized as ‘other’, 9% (84) in acute care facilities, and 2% (15) in schools/daycares. Of the 855 outbreaks where influenza type was reported, 88% (750) were due to influenza A. Among the 307 outbreaks for which the influenza A subtype was reported, 53% were associated with A(H1N1) and 47% with A(H3N2). To date this season, 175 ILI outbreaks have also been reported; 98% (171) in schools/daycares and 2% (4) in facilities categorized as ‘other’.

Number of provinces and territories reporting in week 13: 10 out of 13

Figure 6 - Text equivalent

Surveillance Week	Acute Care Facilities	Long Term Care Facilities	Other	Schools and Daycares	Remote and/or Isolated Communities
35	0	0	0	0	0
36	0	0	0	0	0
37	0	0	0	0	0
38	0	1	0	0	0
39	0	1	0	0	0
40	0	2	0	0	0
41	0	2	1	0	0
42	1	0	0	0	0
43	0	0	1	0	0
44	0	0	1	0	0
45	0	2	4	0	0
46	1	4	0	0	0
47	0	2	1	1	0
48	1	6	2	2	0
49	2	10	1	1	0
50	4	10	4	1	0
51	4	16	11	0	0
52	4	48	15	0	0
1	17	86	40	0	0
2	12	92	36	0	0
3	10	52	7	1	0
4	5	50	19	3	0
5	5	23	9	0	0
6	8	17	25	4	0
7	1	31	12	1	0
8	4	32	6	1	0
9	2	32	7	0	0
10	1	19	3	0	0
11	0	31	12	0	0
12	0	11	4	0	0
13	2	3	0	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 2,333 influenza-associated hospitalizations were reported by participating provinces and territories ^{Footnote 1}.

• 69% of the cases were associated with influenza A.
• Of the 1,036 cases for which subtype was reported, 52% were associated with influenza A(H3N2).
• The highest cumulative hospitalization rates up to week 13 were among adults 65 years of age and older (77/100,000 population) and children under 5 years of age (73/100,000 population).

285 ICU admissions and 102 deaths have been reported.

• 69% of the ICU admissions and 72% of the deaths were associated with influenza A.

Number of provinces and territories reporting in week 13: 4 out of 9

Footnote ‡

Influenza-associated hospitalizations are reported by Alberta, Manitoba, New Brunswick, Newfoundland and Labrador, Northwest Territories, Nova Scotia, Prince Edward Island and Yukon. Only hospitalizations that require intensive medical care are reported by Saskatchewan.

Return to footnote 1 referrer

Figure 7 - Text equivalent

Surveillance Week	0-4 yrs	5-19 yrs	20-44 yrs	45-64 yrs	65+ yrs
35	0.0	0.0	0.0	0.0	0.0
36	0.0	0.0	0.0	0.0	0.2
37	0.0	0.0	0.0	0.1	0.2
38	0.0	0.0	0.0	0.1	0.4
39	0.2	0.0	0.0	0.1	0.6
40	0.2	0.0	0.0	0.1	0.8
41	0.4	0.2	0.1	0.2	1.1
42	0.8	0.2	0.1	0.2	1.3
43	1.0	0.2	0.2	0.3	1.6
44	1.5	0.2	0.2	0.5	2.1
45	1.9	0.4	0.4	0.8	2.8
46	1.9	0.4	0.6	1.1	3.3
47	3.1	0.6	0.8	1.5	4.6
48	5.0	1.1	1.0	1.6	5.7
49	7.1	1.9	1.3	2.0	7.5
50	11.1	3.0	1.8	2.3	10.2
51	14.3	3.7	2.5	3.5	13.6
52	18.7	5.8	3.7	4.5	19.3
1	27.7	6.5	4.8	6.6	28.1
2	33.8	7.6	6.0	8.4	34.5
3	38.8	8.4	7.0	10.0	40.4
4	43.7	9.6	8.2	11.8	45.4
5	52.5	10.7	9.4	13.5	50.9
6	57.5	11.8	10.5	15.0	55.7
7	59.6	12.8	11.2	16.3	59.5
8	62.6	13.7	11.9	17.3	63.4
9	65.3	14.4	12.3	18.4	66.8
10	68.2	15.2	12.9	19.5	71.0
11	70.7	15.4	13.3	20.2	73.7
12	71.2	15.6	13.5	20.5	74.8
13	73.3	16.0	13.8	21.0	76.7

Pediatric Influenza Hospitalizations and Deaths

In week 13, four pediatric (≤16 years of age) laboratory-confirmed influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 8). Since the beginning of March, the weekly number of reported cases have dropped below the 5-year weekly average.

To date this season (weeks 35 to 13):

• 1,207 pediatric hospitalizations have been reported by the IMPACT network, of which 52% (622) were associated with influenza A and 49% (585) with influenza B.
• The largest proportion of hospitalizations (66%) were among children under 5 years of age (Figure 9).
• 203 ICU admissions were reported, of which 58% were associated with influenza A, and 61% were among children under 5 years of age.
• Five pediatric deaths have been reported.

The shaded area represents the maximum and minimum number of cases reported by week from seasons 2014-15 to 2018-19

Figure 8 - Text equivalent

Surveillance week	2019-2020	Average	Min	Max
35	0	0	0	1
36	2	0	0	1
37	0	1	0	2
38	0	1	0	2
39	1	1	0	3
40	0	1	0	2
41	2	1	0	3
42	2	2	0	5
43	1	5	2	12
44	2	5	1	15
45	3	10	2	37
46	6	13	1	41
47	6	13	2	36
48	26	18	2	40
49	23	22	3	47
50	38	29	4	50
51	57	41	5	84
52	104	54	14	89
1	105	55	21	94
2	101	40	12	63
3	81	44	28	64
4	91	53	34	93
5	111	47	25	70
6	111	49	15	79
7	66	59	17	120
8	85	63	25	139
9	57	58	13	153
10	50	55	17	135
11	46	51	18	118
12	26	39	13	89
13	4	32	14	67

Adult Influenza Hospitalizations and Deaths

Surveillance of laboratory-confirmed influenza-associated adult (≥16 years of age) hospitalizations by the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) network began on November 1st  for the 2019-20 season.

To date this season, 787 hospitalizations, 87 intensive care unit admissions, and 42 deaths have been reported (Figure 10).

• The majority of hospitalizations have been due to influenza A (79%), and among those subtyped (166) 92% were influenza A(H1N1).
• Among the 623 cases with influenza A, the largest proportion of hospitalizations were in adults 65 years of age and older (66%). Among the 153 cases with influenza B, 52% were in adults 65 years of age and older, and 28% of cases were between 16 and 34 years of age (Figure 11).
• 90% of hospitalized cases reported at least one type of comorbid condition.

Influenza Strain Characterizations

From September 1, 2019 to March 19, 2020, the National Microbiology Laboratory (NML) has characterized 1,224 influenza viruses (474 A(H1N1), 177 A(H3N2) and 573 influenza B) that were received from Canadian laboratories.

Influenza A(H3N2)

Over recent years, circulating strains of A(H3N2) have evolved, and are increasingly difficult to characterize by hemagglutination inhibition (HI) assay. Genetic characterization is established by sequencing the hemagglutinin (HA) gene of the influenza viruses to compare their genetic properties.

Antigenic Characterization:

Among the 55 influenza A(H3N2) viruses antigenically characterized to date, the majority (80%) showed reduced titer by HI assay to A Kansas/14/2017 using antiserum raised against egg-propagated A Kansas/14/2017. Eleven viruses were characterized as A Kansas/14/2017-like (Figure 12a).

Genetic Characterization:

Nearly all (98%) of the 160 A(H3N2) viruses genetically characterized this season belonged to genetic group 3C.2a1b based on sequence analysis of the HA gene. Three viruses belonged to the genetic group 3C.3a (Figure 13).

Group 3C.2a1b viruses analysed represent:

• 92% (35 out of 38) viruses that were also antigenically characterized.
• 100% (122 out of 122) viruses which did not grow to sufficient hemagglutination titer for antigenic characterization by HI assay.

A/Kansas/14/2017 belongs to genetic group 3C.3a and is the influenza A(H3N2) component of the 2019-20 Northern Hemisphere influenza vaccine.

Influenza A(H1N1)

Among the 474 A(H1N1) viruses characterized to date, 53% were antigenically similar to A/Brisbane/02/2018 by HI testing using antiserum raised against egg-propagated A/Brisbane/02/2018 (Figure 12 b).

A/Brisbane/02/2018 is the influenza A(H1N1) component of the 2019-20 Northern Hemisphere influenza vaccine.

Influenza B

Antigenic Characterization:

Among the 182 influenza B viruses antigenically characterized this season, the vast majority (180) belonged to the B/Victoria lineage. Two viruses were antigenically characterized as similar to B/Phuket/3073/2013 (B/Yamagata lineage).

The majority (89%, 161) of B/Victoria lineage viruses showed reduced titer by HI assay to B/Colorado/06/2017 using antiserum raised against cell culture-propagated B/Colorado/06/2017 (Figure 12c).

Sequence analysis of 150 B/Victoria lineage viruses with reduced titre to B/Colorado/06/2017 showed that 100% had a three amino acid deletion (162-164) in the HA gene and belong to the genetic subclade V1A.3 (3Del). Sequencing is pending for the remaining viruses.

Genetic Characterization:

Genetic characterization was also performed on 391 B/Victoria lineage viruses. All of these viruses had a three amino acid deletion (162-164) in the HA gene and belong to the genetic subclade V1A.3 (3Del).

To date, 100% (541) of influenza B/Victoria viruses genetically characterized belong to the genetic subclade V1A.3 (3Del) (Fig 13b). Viruses in this genetic subclade are antigenically distinct from the vaccine strain B/Colorado/06/2017, which belongs to genetic subclade V1A.1 (2Del).

The recommended influenza B components for the 2019-20 Northern Hemisphere influenza vaccine are B/Colorado/06/2017 (Victoria lineage) and B/Phuket/3073/2013 (Yamagata lineage). B/Phuket/3073/2013 is included in the quadrivalent influenza vaccine. The vaccine strain B/Colorado/06/2017 belongs to genetic subclade V1A.1.

Antiviral Resistance

The National Microbiology Laboratory (NML) also tests influenza viruses received from Canadian laboratories for antiviral resistance. From September 1, 2019 to March 19, 2020, the following results were reported:

Oseltamivir:

669 influenza viruses (155 A(H3N2), 251 A(H1N1) and 263 B) were tested for resistance to oseltamivir:

• All influenza A(H3N2) and B viruses were sensitive to oseltamivir.
• Among the A(H1N1) viruses tested, 250 (99.6%) were sensitive to oseltamivir and one virus was resistant to oseltamivir with the H275Y mutation in the neuraminidase gene.

Zanamivir:

669 influenza viruses (155 A(H3N2), 251 A(H1N1) and 263 B) were tested for resistance to zanamivir:

• All influenza viruses tested were sensitive to zanamivir.

Amantadine:

High levels of resistance to amantadine persist among influenza A(H1N1) and influenza A(H3N2) viruses. All viruses tested this season were resistant.

Vaccine Monitoring

Vaccine monitoring refers to activities related to the monitoring of influenza vaccine coverage and effectiveness.

Vaccine Coverage

The Seasonal Influenza Immunization Coverage Survey is an annual telephone survey conducted between January and February that collects information from Canadians on whether they received the annual seasonal influenza vaccine that season. Vaccine coverage is measured as the percentage of people who received the influenza vaccine in a specific influenza season.

In the 2019-20 influenza season, coverage was similar to the 2018-19 season, at:

• 34% among adults aged 18 to 64 years.
  • 30% among adults aged 18-64 without chronic diseases.
  • 44% among adults aged 18 to 64 years with chronic diseases.
• 70% among seniors (aged 65 years and older).

Table 2 – Influenza vaccine coverage among adults (n=3,026)^{Table 2 - Footnote *} by age group gender^{Table 2 - Footnote ‡} and medical conditions^{Table 2 - Footnote †}, Seasonal Influenza Vaccination Coverage Survey, Canada, September 2019 – February 2020

Age group (years)	All		Male		Female
	N	Vaccine Coverage % (95% CI)	N	Vaccine Coverage % (95% CI)	N	Vaccine Coverage % (95% CI)
All adults (≥18)	3023	41.8 (39.7-43.9)	1320	37.2 (34.1-40.2)	1691	46.1 (43.2-49.0)
18-64	2234	34.1 (31.8-36.5)	1005	29.8 (26.5-33.1)	1218	38.4 (35.1-41.7)
with chronic diseases	668	43.6 (39.0-48.1)	268	38.3 (31.5-45.2)	397	47.9 (41.7-54.0)
without chronic diseases	1558	30.0 (27.3-32.7)	732	26.7 (22.9-30.5)	818	33.5 (29.6-37.3)
≥65	789	70.3 (66.7-73.8)	315	67.2 (61.5-72.9)	473	72.7 (68.3-77.1)
CI: 95% confidence interval Footnote * 3 people did not recall whether they had received the influenza vaccine and were excluded from coverage estimates. Return to table 2 footnote * referrer Footnote ‡ 4 people did not disclose their gender and 8 people did not identify themselves as male nor female. They were excluded from stratified analysis. Return to table 2 footnote ‡ referrer Footnote † 8 people who were 18-64 years old did not disclose whether they had any chronic medical conditions (CMC) and were excluded from stratified analysis. Return to table 2 footnote † referrer

Vaccine Effectiveness

The Canadian Sentinel Practitioner Surveillance Network (SPSN) provides estimates of the effectiveness of the seasonal influenza vaccine in preventing medically-attended illness due to laboratory-confirmed influenza among Canadians.

Based on data collected between November 1, 2019 and February 1, 2020, vaccine effectiveness (VE) was estimated to be 58% for any influenza, 44% for influenza A(H1N1), 62% for influenza A(H3N2), and 69% for influenza B. Substantial protection was observed among children 1 to 19 years of age against both influenza A and B. A good level of protection was also observed among working age adults (20-64 yrs) across all influenza types (Table 2). VE among adults 65 years and older, although imprecise due to small numbers, was lower at 18% (95% CI -59 to 58). The SPSN interim estimates are published and available online.

More information on the network and past VE findings can be viewed on the SPSN website.

Updated influenza vaccine effectiveness estimates will be published at the end of the 2019/2020 influenza season. At that time, sufficient data will likely be available to estimate VE by age-group, including adults 65 years and older with greater precision, as well as for influenza A subtypes.

Table 3 - Vaccine effectiveness estimates against medically-attended influenza illness, SPSN, November 1, 2019, to February 1, 2020

	All ages		1-19 years	20-64 years
	VE(%) (CI)Table 3 - Footnote *	N	VE(%) (CI)Table 3 - Footnote *	VE(%) (CI)Table 3 - Footnote *
All Influenza	58 (47, 66)	2808	74 (59, 84)	55 (41, 66)
Influenza A	49 (34, 60)	2128	70 (44, 84)	45 (25, 59)
Influenza A(H1N1)	44 (26, 58)	1948	-	-
Influenza A(H3N2)	62 (37, 77)	1561	-	-
Influenza B	69 (57, 77)	2080	77 (59, 87)	68 (51, 79)
Footnote * adjusted for age group, province, specimen collection interval and calendar time Return to table 2 footnote * referrer