FluWatch report: February 16 to 22, 2020 (week 08)

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Organization: Public Health Agency of Canada

Date published: 2020-02-28

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Overall Summary

  • Influenza activity remained high in week 08; the majority of indicators remained similar or increased slightly from the previous week.
  • Influenza A(H1N1) is currently the dominant influenza A subtype circulating in Canada, representing 78% of subtyped influenza A specimens in week 08. 
  • The highest cumulative hospitalization rates are among children under 5 years of age and adults 65 years of age and older.
  • The Sentinel Practitioner Surveillance Network (SPSN) has published interim estimates of vaccine effectiveness which indicate that the 2019/2020 influenza vaccine has provided substantial protection against medically-attended influenza illness in the early part of the season in Canada. Within-season 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.

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

During week 08, influenza activity was reported in all regions in all reporting provinces and territories. Among these regions, 55% reported sporadic activity, 43% reported localized activity, and 2% reported widespread activity (Figure 1).

Figure 1 – Map of influenza/ILI activity by province and territory, Canada, week 2020-08

Number of Regions Reporting in Week 08: 53 out of 53

Figure 1. Text equivalent follows.

Figure 1 - Text equivalent
Province Influenza Surveillance Region Activity Level
N.L. Eastern Sporadic
N.L. Labrador-Grenfell Localized
N.L. Central Localized
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 Sporadic
N.B. Region 5 Sporadic
N.B. Region 6 Localized
N.B. Region 7 Localized
Que. Nord-est Localized
Que. Québec et Chaudieres-Appalaches Sporadic
Que. Centre-du-Québec Localized
Que. Montréal et Laval Localized
Que. Ouest-du-Québec Localized
Que. Montérégie Sporadic
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 Sporadic
Man. Winnipeg Sporadic
Man. Southern Health Sporadic
Sask. North Sporadic
Sask. Central Sporadic
Sask. South Localized
Alta. North Zone Sporadic
Alta. Edmonton Sporadic
Alta. Central Zone Localized
Alta. Calgary Sporadic
Alta. South Zone Sporadic
B.C. Interior Sporadic
B.C. Fraser Sporadic
B.C. Vancouver Coastal Localized
B.C. Vancouver Island Widespread
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 08, the percentage of laboratory tests positive for influenza was similar to the previous three weeks at 29% and remains similar to the peak percentages reported since late December. Influenza A and B continue to co-circulate.

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

To date this season (weeks 35 to 08), 42,291 laboratory detections of influenza were reported

Detailed information on age and type/subtype has been received for 32,801 laboratory-confirmed influenza cases (Table 1). To date this season (weeks 35 to 08):

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.

Figure 2 - Number of positive influenza tests and percentage of tests positive, by type, subtype and report week, Canada, weeks 2019-35 to 2020-08

Number of Laboratories Reporting in Week 08: 34 out of 36

Figure 2

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)pdm09 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 1742 74 303 1841 15.6 12.9
8 1675 67 241 1466 16.8 11.8

Figure 3 – Distribution of positive influenza specimens by type/subtype and province/territoryFootnote *, Canada, weeks 2019-35 to 2020-08

Figure 3. Text equivalent follows.
Footnote *

Specimens from NWT, YT, and Nvt are sent to reference laboratories in other provinces.

Return to footnote * referrer

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. 2119 220 235 747 1555 3674
Alta. 3256 990 1162 1104 2972 6228
Sask. 1196 0 0 1196 556 1752
Man. 1061 129 102 830 811 1872
Ont. 5625 2208 383 3034 1841 7466
Que. 9948 0 0 9948 9054 19002
N.B. 550 36 22 492 900 1450
N.S. 77 2 1 74 123 200
P.E.I. 76 0 0 76 60 136
N.L. 79 4 31 44 179 258
Y.T. 42 4 8 30 8 50
N.W.T 68 57 10 1 74 142
Nvt. 42 3 3 36 19 61
Canada 24139 3653 1957 17612 18152 42291
PercentageTable Figure 3 - Footnote 2 57% 15% 8% 73% 43% 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 numbers of positive influenza specimens by type, subtype and age group reported through case-based laboratory reporting, Canada, weeks 2019-35 to 2020-08
Age groups
(years)
Cumulative (August 25, 2019 to February 22, 2020)
Influenza A B Influenza A and B
A Total A(H1N1) A(H3N2) A (Un subtyped)Table 1 Footnote 1 Total # %
0-4 2901 305 172 2424 3423 6324 19%
5-19 2004 186 224 1594 5108 7112 22%
20-44 3797 663 280 2854 4443 8240 25%
45-64 3508 666 258 2584 833 4341 13%
65+ 5735 789 801 4145 1049 6784 21%
Total 17945 2609 1735 13601 14856 32801 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 08, 1.5% of visits to healthcare professionals were due to influenza-like illness (ILI) which is below the average for this time of year (Figure 4).

Figure 4 – Percentage of visits for ILI reported by sentinels by report week, Canada, weeks 2019-35 to 2020-08

Number of Sentinels Reporting in Week 08: 79

Figure 4

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 2019-20 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 1.8% 2.4% 1.4% 4.0%
7 1.3% 2.4% 0.9% 3.5%
8 1.5% 2.3% 0.8% 3.4%

FluWatchers

The proportion of FluWatchers participants reporting symptoms of cough and fever increased in week 08 compared to the previous week. In week 08, 3,131 participants reported to FluWatchers, of which 2.8% (86) reported symptoms of cough and fever (Figure 5).

Among the 86 participants who reported cough and fever:

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

Figure 5 - Percentage of participants reporting fever and cough, Canada, weeks 2019-40 to 2020-08

Number of Participants Reporting in Week 08: 3,131

Figure 5. Text equivalent follows.
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%

Online Figure – Geographic distribution of FluWatchers participants reporting cough and fever, Canada, week 2020-08

Click on the map to access the link

map

Influenza Outbreak Surveillance

In week 08, a total of 30 outbreaks were reported: 22 in long term care facilities, three in facilities categorized as ‘other’, which includes facilities such as private personal care homes, correctional facilities, and colleges/universities, four in acute care facilities and one in a school/daycare (Figure 6). In addition, 19 ILI outbreaks were reported: 17 in schools/daycares and 2 in facilities categorized as ‘other’ .

To date this season, a total of 757 laboratory-confirmed influenza outbreaks have been reported; 62% (473) in long-term care facilities, 25% (190) in facilities categorized as ‘other’, 10% (79) in acute care facilities, and 2% (15) in schools/daycares. Of the 720 outbreaks where influenza type was reported, 88% (632) were due to influenza A. Among the 272 outbreaks for which the influenza A subtype was reported, 50% were associated with A(H3N2) and 50% were associated with A(H1N1). To date this season, 140 ILI outbreaks have also been reported; 98%(137) in schools/daycares and 2%(3) in facilities categorized as ‘other’.

Figure 6 – Number of new outbreaks of laboratory-confirmed influenza by report week, Canada, weeks 2019-35 to 2020-08

Number of provinces and territories reporting in week 08: 13 out of 13

Figure 6

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 29 11 1 0
8 4 22 3 1 0

Severe Outcomes Influenza Surveillance

Provincial/Territorial Influenza Hospitalizations and Deaths

To date this season, 1,795 influenza-associated hospitalizations were reported by participating provinces and territories1.

211 ICU admissions and 74 deaths have been reported.

Figure 7 – Cumulative rates of influenza-associated hospitalizations by age-group and surveillance week, Canada, participating provinces and territoriesFootnote 1 weeks 2019-35 to 2020-08

Number of provinces and territories reporting in week 08: 9 out of 9

Figure 7

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 5.9 8.4 34.5
3 38.6 8.4 6.9 10.0 40.4
4 43.0 9.6 8.1 11.8 45.1
5 49.7 10.6 9.1 13.2 49.9
6 53.9 11.5 9.8 14.2 53.5
7 55.6 12.3 10.2 14.8 55.3
8 57.5 12.8 10.4 15.1 56.9

Pediatric Influenza Hospitalizations and Deaths

In week 08, 84 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 due to influenza B remains high; however, in recent weeks, a growing proportion of cases have been due to influenza A.
The elevated number of cases this season compared to previous seasons is likely due to the concurrent circulation of influenza A and B. The 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. The number of hospitalizations with influenza B remains well above average compared to previous seasons.
To date this season (weeks 35 to 08):

Figure 8 – Number of pediatric (≤16 years of age) hospitalizations reported by the IMPACT network, by week, Canada, weeks 2019-35 to 2020-08

Figure 8

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 39 29 4 50
51 60 41 5 84
52 99 54 14 89
1 108 55 21 94
2 101 40 12 63
3 83 44 28 64
4 90 53 34 93
5 117 47 25 70
6 112 49 15 79
7 70 59 17 120
8 84 63 25 139
Figure 9 - Cumulative number of pediatric hospitalizations (≤16 years of age) with influenza by age-group reported by the IMPACT network, Canada, weeks 2019-35 to 2020-08

Figure 9

Figure 9 - Text Description
Age Group Total
0-5 mo 119
6-23 mo 275
2-4 yr 284
5-9 yr 228
10-16 yr 131

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, 627 hospitalizations, 60 intensive care unit admissions, and 28 deaths have been reported (Figure 10).

Figure 10 - Number of adult hospitalizations (≥16 years of age) with influenza reported by the CIRN-SOS network, by week, Canada, weeks 2019-45 to 2020-08

Figure 10

Figure 10 - Text Description
Surveillance Week Number of Hospitalizations
35 No data
36 No data
37 No data
38 No data
39 No data
40 No data
41 No data
42 No data
43 No data
44 No data
45 No data
46 2
47 4
48 9
49 12
50 14
51 35
52 76
1 90
2 66
3 56
4 46
5 51
6 68
7 43
8 42
Figure 11 - Cumulative numbers of adult hospitalizations (≥16 years of age) with influenza, by age-group, reported by the CIRN-SOS network, Canada, weeks 2019-45 to 2020-08

Figure 11

Figure 11 - Text Description
Age Group Total hospitalizations
16-34 yr 65
35-49 yr 56
50-64 yr 112
65-79 yr 205
80+ yr 189

Influenza Strain Characterizations

From September 1, 2019 to February 27, 2020, the National Microbiology Laboratory (NML) has characterized 1157 influenza viruses (406 A(H1N1), 159 A(H3N2) and 433 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 135 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:

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 406 A(H1N1) viruses characterized to date, 52% 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-3Del. Sequencing is pending for the remaining viruses.

Genetic Characterization:

Genetic characterization was also performed on 251 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-3Del. Viruses belonging to genetic subclade V1A-3Del are antigenically distinct from the vaccine strain B/Colorado/06/2017, which belongs to genetic subclade V1A.1.

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.

Figure 12 - Distribution of antigenic phenotypes among characterized influenza viruses, Canada, September 1, 2019 to February 27, 2020

Figure 12

Figure 12 - Text Description
A) Antigenic phenotypes among influenza A(H3N2) viruses
Number of viruses characterized:  55
Antigenic phenotype of A(H3N2) virus Number of viruses Percentage
A/Kansas/14/2017-like 11 20%
Reduced titer to A/Kansas/14/2017 44 80%
B) Antigenic phenotypes among influenza A(H1N1) viruses
Number of viruses characterized:  406
Antigenic phenotype of A(H1N1) virus Number of viruses Percentage
A/Brisbane/02/2018-like 211 52%
Reduced titer to A/Brisbane/02/2018 195 48%
C) Antigenic phenotypes among influenza B viruses
Number of viruses characterized:  182
Antigenic phenotype of influenza B virus Number of viruses Percentage
B/Colorado/06/2017-like 19 10%
Reduced titer to B/Colorado/06/2017 161 88%
B/Phuket/3073/2013-like 2 1%
Figure 13 - Distribution of genetic clades among characterized A(H3N2) influenza viruses, Canada, September 1, 2019 to February 27, 2020

Figure 13

Figure 13 - Text Description
Number of viruses sequenced:  135
Genetic Clade of A(H3N2) virus Number of viruses Percentage
Subclade 3C.2a1b 132 98%
Clade 3C.3a 3 2%

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:

Zanamivir:

553 influenza viruses (147 A(H3N2), 192 A(H1N1) and 214 B) were tested for resistance 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.

Notes

The data in the FluWatch report represent surveillance data available at the time of writing. All data are preliminary and may change as more reports are received.

To learn more about the FluWatch program, see the Overview of influenza monitoring in Canada page.

For more information on the flu, see our Flu (influenza) web page.

We would like to thank all the Fluwatch surveillance partners participating in this year's influenza surveillance program.

This report is available on the Government of Canada Influenza webpage.
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