FluWatch report: February 23 to 29, 2020 (week 09)

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

During week 09, influenza activity was reported in all regions in all reporting provinces and territories. Among these regions, 49% reported sporadic activity, 49% reported localized activity, and 2% reported widespread activity (Figure 1).

Figure 1 - Text equivalent

Province	Influenza Surveillance Region	Activity Level
N.L.	Eastern	Sporadic
N.L.	Labrador-Grenfell	Sporadic
N.L.	Central	Sporadic
N.L.	Western	Sporadic
P.E.I.	Prince Edward Island	Localized
N.S.	Zone 1 - Western	Localized
N.S.	Zone 2 - Northern	Localized
N.S.	Zone 3 - Eastern	Sporadic
N.S.	Zone 4 - Central	Localized
N.B.	Region 1	Sporadic
N.B.	Region 2	Localized
N.B.	Region 3	Localized
N.B.	Region 4	Localized
N.B.	Region 5	Localized
N.B.	Region 6	Localized
N.B.	Region 7	Localized
Que.	Nord-est	Localized
Que.	Québec et Chaudieres-Appalaches	Localized
Que.	Centre-du-Québec	Localized
Que.	Montréal et Laval	Sporadic
Que.	Ouest-du-Québec	Sporadic
Que.	Montérégie	Localized
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	Localized
Man.	Northern Regional	Sporadic
Man.	Prairie Mountain	Sporadic
Man.	Interlake-Eastern	Localized
Man.	Winnipeg	Localized
Man.	Southern Health	Sporadic
Sask.	North	Sporadic
Sask.	Central	Sporadic
Sask.	South	Sporadic
Alta.	North Zone	Sporadic
Alta.	Edmonton	Localized
Alta.	Central Zone	Localized
Alta.	Calgary	Sporadic
Alta.	South Zone	Sporadic
B.C.	Interior	Localized
B.C.	Fraser	Widespread
B.C.	Vancouver Coastal	Localized
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	Sporadic
Nvt.	Kitimeot	Sporadic

Laboratory-Confirmed Influenza Detections

In week 09, the percentage of laboratory tests positive for influenza decreased slightly compared to the previous five weeks to 26%. Influenza A circulation remains high, while influenza B circulation has decreased in recent weeks.

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

• The percentage of tests positive for influenza A was 17% in week 09, which is similar to the previous eight weeks.
• Among subtyped influenza A detections, influenza A(H1N1) accounted for 85% of detections, a slight increase in proportion compared to the previous four weeks.
• The percentage of tests positive for influenza B continued to decrease to 9% in week 09. This continues to be  higher than avereage for this time of year.

To date this season (weeks 35 to 08), all influenza types and subtypes have circulated. Among the 46,038 laboratory detections of influenza reported:

• 58% (26,571) were influenza A.
• Among subtyped influenza A detections (6,124), A(H1N1) is the predominant subtype this season (65%).

Detailed information on age and type/subtype has been received for 35,356 laboratory-confirmed influenza cases (Table 1). To date this season (weeks 35 to 09):

• Cases of influenza A(H1N1) (2,851) were primarily in adults; 25% in adults 20-44 years, 26% in adults 45-64 years and30% of cases in adults 65 years of age and older.
• Among cases of influenza A(H3N2) (1,868), the largest proportion was in adults 65 years of age and older (47%).
• Cases of influenza B (15,761) were primarily in younger age groups; 58% under 19 years of age and 29% 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 09: 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	1587	131	414	1418	16.2	10.3
4	1736	126	368	1952	15.2	12.7
5	1987	96	437	2269	16.0	13.7
6	1982	70	337	2265	15.6	14.1
7	1747	76	315	1851	15.5	12.8
8	1773	71	244	1537	16.4	11.5
9	1862	53	292	1225	16.7	8.8

Figure 3 - Text equivalent

ProvincesTable Figure 3 - Footnote 1	Cumulative (August 25, 2019 to February 22, 2020)
	A Total	A(H1N1)	A(H3N2)	A(UnS)Table Figure 3 - Footnote 3	B Total	A & B Total
B.C.	2455	249	235	929	1734	4189
Alta.	3498	1113	1186	1199	3063	6561
Sask.	1370	59	102	1209	700	2070
Man.	1220	143	111	966	835	2055
Ont.	5838	2318	400	3120	1961	7799
Que.	11074	0	0	11074	9543	20617
N.B.	697	51	24	622	1058	1755
N.S.	88	3	2	83	142	230
P.E.I.	76	0	0	76	60	136
N.L.	93	4	32	57	243	336
Y.T.	45	4	8	30	8	53
N.W.T	72	60	11	1	90	162
Nvt.	45	3	6	36	30	75
Canada	26571	4007	2117	19402	19467	46038
PercentageTable Figure 3 - Footnote 2	58%	15%	8%	73%	42%	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 2020-09

Age groups (years)	Cumulative (August 25, 2019 to February 29, 2020)
	Influenza A				B	Influenza A and B
	A Total	A(H1N1)	A(H3N2)	A (Un subtyped) Table 1 Footnote 1	Total	#	%
0-4	3222	343	191	2688	3689	6911	20%
5-19	2248	213	240	1795	5432	7680	22%
20-44	4039	708	293	3038	4604	8643	24%
45-64	3794	731	269	2794	887	4681	13%
65+	6292	856	875	4561	1149	7441	21%
Total	19595	2851	1868	14876	15761	35356	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 09, 1.5% of visits to healthcare professionals were due to influenza-like illness (ILI) which remains below the average for this time of year (Figure 4).

Number of Sentinels Reporting in week 09: 85

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	1.5%	2.3%	0.9%	3.1%
10	#N/A	2.0%	1.0%	2.8%
11	#N/A	1.9%	1.1%	2.8%
12	#N/A	1.6%	0.6%	2.6%
13	#N/A	1.6%	1.1%	2.6%
14	#N/A	1.7%	1.1%	3.0%
15	#N/A	1.3%	0.9%	1.9%
16	#N/A	1.2%	0.8%	1.7%
17	#N/A	1.2%	0.7%	1.7%
18	#N/A	1.3%	0.5%	2.0%
19	#N/A	0.9%	0.6%	1.3%
20	#N/A	1.1%	0.6%	1.5%
21	#N/A	0.9%	0.5%	1.3%
22	#N/A	0.7%	0.3%	1.0%
23	#N/A	0.8%	0.6%	1.0%
24	#N/A	0.7%	0.6%	1.0%
25	#N/A	0.6%	0.4%	0.8%
26	#N/A	0.8%	0.5%	1.4%
27	#N/A	0.6%	0.5%	0.7%
28	#N/A	0.7%	0.5%	1.3%
29	#N/A	0.9%	0.6%	1.7%
30	#N/A	0.6%	0.2%	0.9%
31	#N/A	0.4%	0.2%	0.6%
32	#N/A	0.8%	0.3%	1.2%
33	#N/A	0.7%	0.4%	1.3%
34	#N/A	0.7%	0.4%	1.5%

FluWatchers

The proportion of FluWatchers participants reporting symptoms of cough and fever decreased in week 09 compared to the previous week. In week 09, 3,032 participants reported to FluWatchers, of which 2.4% (73) reported symptoms of cough and fever (Figure 5).

Among the 73 participants who reported cough and fever:

• 27% consulted a healthcare professional;
• 78% reported days missed from work or school, resulting in a combined total of 182 missed days of work or school.

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

Number of participants reporting in week 9: 3,032

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	0.0%
11	0.0%
12	0.0%
13	0.0%
14	0.0%
15	0.0%
16	0.0%
17	0.0%
18	0.0%

Online Figure - Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2020-09

Click on the map to access the link

Influenza Outbreak Surveillance

In week 09, a total of 27 outbreaks were reported: 19 in long term care facilities, six in facilities categorized as 'other', which includes facilities such as private personal care homes, correctional facilities, and colleges/universities, and two in acute care facilities (Figure 6). In addition, six ILI outbreaks were reported in schools/daycares.

To date this season, a total of 796 laboratory-confirmed influenza outbreaks have been reported; 63% (503) in long-term care facilities, 25% (197) in facilities categorized as ‘other’, 10% (81) in acute care facilities, and 2% (15) in schools/daycares. Of the 752 outbreaks where influenza type was reported, 88% (659) were due to influenza A. Among the 284 outbreaks for which the influenza A subtype was reported, 51% were associated with A(H1N1) and 49% with A(H3N2). To date this season, 146 ILI outbreaks have also been reported; 98% (143) in schools/daycares and 2% (3) in facilities categorized as ‘other’.

Number of provinces and territories reporting in week 09: 13 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	35	0	0
3	10	51	7	1	0
4	5	50	19	3	0
5	5	23	9	0	0
6	8	16	25	4	0
7	1	31	11	1	0
8	4	31	4	1	0
9	2	19	6	0	0
10	0	0	0	0	0
11	0	0	0	0	0
12	0	0	0	0	0
13	0	0	0	0	0
14	0	0	0	0	0
15	0	0	0	0	0
16	0	0	0	0	0
17	0	0	0	0	0
18	0	0	0	0	0
19	0	0	0	0	0
20	0	0	0	0	0
21	0	0	0	0	0
22	0	0	0	0	0
23	0	0	0	0	0
24	0	0	0	0	0
25	0	0	0	0	0
26	0	0	0	0	0
27	0	0	0	0	0
28	0	0	0	0	0
29	0	0	0	0	0
30	0	0	0	0	0
31	0	0	0	0	0
32	0	0	0	0	0
33	0	0	0	0	0
34	0	0	0	0	0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 1,986 influenza-associated hospitalizations were reported by participating provinces and territories ^{Footnote 1}.

• 67% of the cases were associated with influenza A.
• Of the 902 cases for which subtype was reported, 58% were associated with influenza A(H3N2).
• The highest cumulative hospitalization rates up to week 09 were among children under 5 years of age and adults 65 years of age and older (63/100,000 population).

240 ICU admissions and 81 deaths have been reported.

• 67% of the ICU admissions and 68% of the deaths were associated with influenza A.

Number of provinces and territories reporting in week 09: 9 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	52.3	10.7	9.4	13.5	50.8
6	57.3	11.8	10.4	14.9	55.6
7	59.2	12.7	11.0	16.0	58.1
8	61.1	13.3	11.5	16.6	61.0
9	62.8	13.8	11.6	17.2	62.6

Pediatric Influenza Hospitalizations and Deaths

In week 09, 58 pediatric (≤16 years of age) laboratory-confirmed influenza-associated hospitalizations were reported by the Immunization Monitoring Program Active (IMPACT) network (Figure 8). The number of cases has been following a downward trend since week 5, with an approximately equal proportion of cases of influenza A and B.

A greater number of total pediatric hospitalizations with influenza have been reported this season compared to the same period during the past 9 seasons. The elevated number of cases this season compared to previous seasons is likely due to the concurrent circulation of influenza A and B in the early part of the influenza season, as well as an above average number of hospitalizations with influenza B. In addition, t he number of influenza A-associated pediatric hospitalizations is above the average for this time of year, which is expected when A(H1N1) is the predominant circulating virus.

To date this season (weeks 35 to 09):

• 1,091 pediatric hospitalizations have been reported by the IMPACT network, of which 51% (561) were associated with influenza A and 49% (530) with influenza B.
• The largest proportion of hospitalizations (66%) were among children under 5 years of age (Figure 9).
• 164 ICU admissions were reported, of which 52% were associated with influenza A, and 64% were among children under 5 years of age.
• Less than 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	60	41	5	84
52	99	54	14	89
1	106	55	21	94
2	101	40	12	63
3	83	44	28	64
4	89	53	34	93
5	117	47	25	70
6	111	49	15	79
7	71	59	17	120
8	84	63	25	139
9	58	58	13	153

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, 690 hospitalizations, 71 intensive care unit admissions, and 32 deaths have been reported (Figure 10).

• The majority of hospitalizations have been due to influenza A (80%), and among those subtyped (163) 91% were influenza A(H1N1).
• Among the 555 cases with influenza A, the largest proportion of hospitalizations were in adults 65 years of age and older (67%). Among the 132 cases with influenza B, 49% were in adults 65 years of age and older, and 30% of cases were between 16 and 34 years of age (Figure 11).
• 89% of hospitalized cases reported at least one type of comorbid condition.

Influenza Strain Characterizations

From September 1, 2019 to March 5, 2020, the National Microbiology Laboratory (NML) has characterized 1,087 influenza viruses (474 A(H1N1), 177 A(H3N2) and 436 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 254 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% (404) 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 February 27, 2020, the following results were reported:

Oseltamivir:

554 influenza viruses (148 A(H3N2), 192 A(H1N1) and 214 B) were tested for resistance to oseltamivir:

• All influenza A(H3N2) and B viruses were sensitive to oseltamivir.
• Among the A(H1N1) viruses tested, 191 (99%) were sensitive to oseltamivir and one virus was resistant to oseltamivir with the H275Y mutation in the neuraminidase gene.

Zanamivir:

553 influenza viruses (147 A(H3N2), 192 A(H1N1) and 214 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 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 2 - 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 2 - Footnote *	N	VE(%) (CI)Table 2 - Footnote *	VE(%) (CI)Table 2 - 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)
CI: 95% confidence interval Footnote * adjusted for age group, province, specimen collection interval and calendar time Return to table 2 footnote * referrer

Vaccine Coverage

Influenza vaccine coverage estimates for the 2019-20 season are anticipated to be available in March 2020.