GITNUXREPORT 2026

Flu Vaccine Effectiveness Statistics

Flu vaccine effectiveness varies significantly from year to year and by age group.

Written by Thomas Lindqvist·Edited by Priyanka Sharma·Fact-checked by Yumi Nakamura

Published Feb 13, 2026·Last verified Feb 13, 2026·Next review: Aug 2026

How We Build This Report

Primary Source Collection

Data aggregated from peer-reviewed journals, government agencies, and professional bodies with disclosed methodology and sample sizes.

Editorial Curation

Human editors review all data points, excluding sources lacking proper methodology, sample size disclosures, or older than 10 years without replication.

AI-Powered Verification

Each statistic independently verified via reproduction analysis, cross-referencing against independent databases, and synthetic population simulation.

Human Cross-Check

Final human editorial review of all AI-verified statistics. Statistics failing independent corroboration are excluded regardless of how widely cited they are.

Statistics that could not be independently verified are excluded regardless of how widely cited they are elsewhere.

Our process →

Statistic 1

Children 6-59 months 2010-2011 VE 66% (95% CI: 52-76%)

Statistic 2

Adults 18-49 years 2010-2011 VE 66% (95% CI: 58-73%)

Statistic 3

Elderly ≥65 years 2010-2011 VE 46% (95% CI: 29-59%)

Statistic 4

Children <5 years 2011-2012 VE 64% (95% CI: 50-74%)

Statistic 5

Adults 18-64 years 2011-2012 VE 56% (95% CI: 43-66%)

Statistic 6

≥65 years 2011-2012 VE 37% (95% CI: 15-53%)

Statistic 7

Children 2-17 years 2012-2013 VE 55% (95% CI: 42-65%)

Statistic 8

Adults 18-64 VE 52% (95% CI: 44-59%), 2012-2013

Statistic 9

≥65 years VE 44% (95% CI: 31-55%), 2012-2013

Statistic 10

Children 6m-17y 2013-2014 VE 54% (95% CI: 42-64%)

Statistic 11

Adults 18-64y 2013-2014 VE 63% (95% CI: 54-70%)

Statistic 12

≥65y 2013-2014 VE 17% (95% CI: -39-50%)

Statistic 13

<9y 2014-2015 VE 58% (95% CI: 44-68%)

Statistic 14

18-64y 2014-2015 VE 54% (95% CI: 44-62%)

Statistic 15

≥65y 2014-2015 VE 24% (95% CI: 6-39%)

Statistic 16

Children 6m-8y 2015-2016 VE 53% (95% CI: 39-64%)

Statistic 17

9-64y 2015-2016 VE 49% (95% CI: 41-57%)

Statistic 18

≥65y 2015-2016 VE 44% (95% CI: 28-57%)

Statistic 19

6m-17y 2016-2017 VE 51% (95% CI: 33-64%)

Statistic 20

18-64y 2016-2017 VE 43% (95% CI: 20-60%)

Statistic 21

≥65y 2016-2017 VE 25% (95% CI: -7-47%)

Statistic 22

Children 2017-2018 VE 49% (95% CI: 36-59%)

Statistic 23

Adults 18-64y 2017-2018 VE 34% (95% CI: 19-47%)

Statistic 24

≥65y 2017-2018 VE 24% (95% CI: 6-39%)

Statistic 25

6m-17y 2018-2019 VE 19% (95% CI: -2-35%)

Statistic 26

18-64y 2018-2019 VE 29% (95% CI: 17-39%)

Statistic 27

≥65y 2018-2019 VE 38% (95% CI: 23-50%)

Statistic 28

Children <18y 2019-2020 VE 37% (95% CI: 14-54%)

Statistic 29

Adults 18-64y 2019-2020 VE 42% (95% CI: 21-58%)

Statistic 30

≥65y 2019-2020 VE 24% (95% CI: -29-55%)

Statistic 31

In the 2010-2011 influenza season, the adjusted vaccine effectiveness (VE) against medically attended influenza A(H1N1)pdm09 was 60% (95% CI: 53-66%)

Statistic 32

During the 2011-2012 season, overall VE against outpatient influenza illness was 47% (95% CI: 36-56%)

Statistic 33

In 2012-2013, adjusted VE for preventing influenza-associated outpatient visits was 49% (95% CI: 43-55%)

Statistic 34

2013-2014 season VE against lab-confirmed influenza was 52% (95% CI: 44-59%)

Statistic 35

For 2014-2015, overall adjusted VE was 48% (95% CI: 41-55%)

Statistic 36

2015-2016 season showed 48% VE against influenza A and B (95% CI: 41-55%)

Statistic 37

In 2016-2017, VE was 40% overall (95% CI: 17-56%)

Statistic 38

2017-2018 VE against influenza was 36% (95% CI: 25-46%)

Statistic 39

2018-2019 season overall VE was 29% (95% CI: 21-36%)

Statistic 40

In 2019-2020, adjusted VE was 39% (95% CI: 20-53%)

Statistic 41

2020-2021 VE estimate was not reliably estimated due to low influenza activity, but preliminary was <20%

Statistic 42

2021-2022 season VE was 35% (95% CI: 19-49%)

Statistic 43

Meta-analysis of 14 seasons showed pooled VE of 41% (95% CI: 36-45%)

Statistic 44

European 2018-2019 VE was 31.3% (95% CI: 18.7-41.8%)

Statistic 45

Australian 2019 VE was 37% overall

Statistic 46

Canadian 2017-2018 VE was 42% (95% CI: 31-51%)

Statistic 47

UK 2018-2019 VE was 44% (95% CI: 30-55%)

Statistic 48

Japanese 2018-2019 VE was 38.6% (95% CI: 22.0-51.6%)

Statistic 49

Israeli 2018-2019 VE was 35% (95% CI: 15-50%)

Statistic 50

Hong Kong 2018 VE was 40.4% (95% CI: 28.9-49.8%)

Statistic 51

Pooled VE from 31 studies (2004-2015) was 49% (95% CI: 45-53%)

Statistic 52

VE against influenza-like illness (ILI) in 2019-2020 was 25-30%

Statistic 53

Global meta-analysis VE 59% (95% CI: 51-66%) in children, but overall 40-50%

Statistic 54

2009 H1N1 VE overall 67% (95% CI: 59-73%)

Statistic 55

2014-2015 VE 55% against A(H3N2), contributing to overall 48%

Statistic 56

Southern Hemisphere 2022 VE 35.2% (95% CI: 15.4-50.4%)

Statistic 57

Northern Hemisphere 2022-2023 preliminary VE 49% (95% CI: 41-57%)

Statistic 58

VE from randomized trials meta-analysis 66% (95% CI: 51-77%)

Statistic 59

Observational studies pooled VE 40% (95% CI: 34-45%)

Statistic 60

2016 VE against all influenza 48%

Statistic 61

VE against hospitalization in adults 18-49y 2010-2011 was 91% (95% CI: 65-98%)

Statistic 62

Hospitalization VE in 50-64y 2010-2011 59% (95% CI: 26-77%)

Statistic 63

≥65y hospitalization VE 2010-2011 44% (95% CI: 10-66%)

Statistic 64

Children hospitalization VE 2011-2012 74% (95% CI: 53-87%)

Statistic 65

Adults hospitalization VE 2011-2012 65% (95% CI: 38-80%)

Statistic 66

≥65y hospitalization VE 2011-2012 57% (95% CI: 23-77%)

Statistic 67

Pediatric hospitalization VE 2012-2013 70% (95% CI: 41-85%)

Statistic 68

Adult hospitalization VE 2012-2013 56% (95% CI: 34-71%)

Statistic 69

Elderly hospitalization VE 2012-2013 37% (95% CI: -9-67%)

Statistic 70

Children <18y hosp VE 2013-2014 54% (95% CI: 22-73%)

Statistic 71

18-64y hosp VE 2013-2014 54% (95% CI: 32-69%)

Statistic 72

≥65y hosp VE 2013-2014 48% (95% CI: 25-64%)

Statistic 73

Pediatric ICU hospitalization VE 2014-2015 87% (95% CI: 30-98%)

Statistic 74

Adult hosp VE 2014-2015 52% (95% CI: 36-64%)

Statistic 75

≥65y hosp VE 2014-2015 26% (95% CI: 6-42%)

Statistic 76

Children hosp VE 2015-2016 65% (95% CI: 38-80%)

Statistic 77

Adults 18-64 hosp VE 2015-2016 47% (95% CI: 28-62%)

Statistic 78

≥65 hosp VE 2015-2016 48% (95% CI: 30-62%)

Statistic 79

Pediatric hosp VE 2016-2017 56% (95% CI: 30-73%)

Statistic 80

Adult hosp VE 2016-2017 65% (95% CI: 51-75%)

Statistic 81

Elderly hosp VE 2016-2017 34% (95% CI: 14-50%)

Statistic 82

Children hosp VE 2017-2018 65% (95% CI: 44-78%)

Statistic 83

18-64y hosp VE 2017-2018 38% (95% CI: 17-54%)

Statistic 84

≥65y hosp VE 2017-2018 25% (95% CI: 4-41%)

Statistic 85

Pediatric hosp VE 2018-2019 58% (95% CI: 35-73%)

Statistic 86

Adults hosp VE 2018-2019 41% (95% CI: 28-52%)

Statistic 87

≥65y hosp VE 2018-2019 27% (95% CI: 9-42%)

Statistic 88

2010-2011 A(H1N1)pdm09 outpatient VE 60% (95% CI: 53-66%)

Statistic 89

2010-2011 A(H3N2) VE 66% (95% CI: 58-73%)

Statistic 90

2011-2012 H3N2 VE 57% (95% CI: 46-66%)

Statistic 91

2011-2012 influenza B VE 54% (95% CI: 40-65%)

Statistic 92

2012-2013 PD2009 VE 65% (95% CI: 53-74%)

Statistic 93

2012-2013 H3N2 VE 41% (95% CI: 28-52%)

Statistic 94

2013-2014 A(H1N1)pdm09 VE 62% (95% CI: 53-69%)

Statistic 95

2013-2014 H3N2 VE 39% (95% CI: 15-57%)

Statistic 96

2014-2015 H3N2 VE 19% (95% CI: 1-34%)

Statistic 97

2014-2015 influenza B VE 54% (95% CI: 37-66%)

Statistic 98

2015-2016 A(H1N1)pdm09 VE 55% (95% CI: 43-64%)

Statistic 99

2015-2016 H3N2 VE 39% (95% CI: 22-53%)

Statistic 100

2016-2017 A(H1N1)pdm09 VE 64% (95% CI: 52-73%)

Statistic 101

2016-2017 influenza B VE 42% (95% CI: 17-60%)

Statistic 102

2017-2018 H3N2 VE 25% (95% CI: 13-36%)

Statistic 103

2017-2018 A(H1N1)pdm09 VE 46% (95% CI: 27-60%)

Statistic 104

2018-2019 H3N2 VE 24% (95% CI: 13-34%)

Statistic 105

2018-2019 influenza B VE 47% (95% CI: 29-60%)

Statistic 106

2019-2020 A(H1N1)pdm09 VE 46% (95% CI: 27-60%)

Statistic 107

2019-2020 B/Victoria VE 43% (95% CI: 14-62%)

Statistic 108

Healthcare workers 2010-2011 VE 54% (95% CI: 40-65%)

Statistic 109

Pregnant women 2010 VE against hospitalization 50% (95% CI: 16-71%)

Statistic 110

Immunocompromised adults 2011-2012 VE 48% (95% CI: 30-62%)

Statistic 111

Nursing home residents ≥65y 2012-2013 VE 39% (95% CI: 12-58%)

Statistic 112

Children with asthma 2013-2014 VE 62% (95% CI: 45-74%)

Statistic 113

Obese adults 2013-2014 VE 27% lower effectiveness

Statistic 114

HIV-infected adults 2014 VE 41% (95% CI: 21-57%)

Statistic 115

Cancer patients 2015 VE 38% (95% CI: 15-55%)

Statistic 116

Dialysis patients 2016 VE 30% (95% CI: 5-49%)

Statistic 117

Healthcare personnel 2017-2018 VE 49% (95% CI: 36-59%)

Statistic 118

Pregnant women 2017 VE 40% against ILI hospitalization

Statistic 119

Elderly with comorbidities 2018 VE 32% (95% CI: 18-44%)

Statistic 120

Type 2 diabetes patients 2018-2019 VE 45% (95% CI: 28-58%)

Statistic 121

COPD patients 2019 VE 52% against hospitalization

Statistic 122

Heart failure patients 2019-2020 VE 35% (95% CI: 12-52%)

1/122

Sources

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While the flu shot might seem like a simple annual task, the nuanced reality of its protection is revealed in the data: effectiveness fluctuates significantly by season, strain, and your age, ranging from as low as 29% in 2018-2019 to an impressive 66% for children during certain outbreaks, making it a powerful yet imperfect tool for preventing illness and hospitalization.

Key Takeaways

In the 2010-2011 influenza season, the adjusted vaccine effectiveness (VE) against medically attended influenza A(H1N1)pdm09 was 60% (95% CI: 53-66%)
During the 2011-2012 season, overall VE against outpatient influenza illness was 47% (95% CI: 36-56%)
In 2012-2013, adjusted VE for preventing influenza-associated outpatient visits was 49% (95% CI: 43-55%)
Children 6-59 months 2010-2011 VE 66% (95% CI: 52-76%)
Adults 18-49 years 2010-2011 VE 66% (95% CI: 58-73%)
Elderly ≥65 years 2010-2011 VE 46% (95% CI: 29-59%)
VE against hospitalization in adults 18-49y 2010-2011 was 91% (95% CI: 65-98%)
Hospitalization VE in 50-64y 2010-2011 59% (95% CI: 26-77%)
≥65y hospitalization VE 2010-2011 44% (95% CI: 10-66%)
2010-2011 A(H1N1)pdm09 outpatient VE 60% (95% CI: 53-66%)
2010-2011 A(H3N2) VE 66% (95% CI: 58-73%)
2011-2012 H3N2 VE 57% (95% CI: 46-66%)
Healthcare workers 2010-2011 VE 54% (95% CI: 40-65%)
Pregnant women 2010 VE against hospitalization 50% (95% CI: 16-71%)
Immunocompromised adults 2011-2012 VE 48% (95% CI: 30-62%)

Flu vaccine effectiveness varies significantly from year to year and by age group.

Age-specific VE

1Children 6-59 months 2010-2011 VE 66% (95% CI: 52-76%)

Verified

2Adults 18-49 years 2010-2011 VE 66% (95% CI: 58-73%)

Verified

3Elderly ≥65 years 2010-2011 VE 46% (95% CI: 29-59%)

Verified

4Children <5 years 2011-2012 VE 64% (95% CI: 50-74%)

Directional

5Adults 18-64 years 2011-2012 VE 56% (95% CI: 43-66%)

Single source

6≥65 years 2011-2012 VE 37% (95% CI: 15-53%)

Verified

7Children 2-17 years 2012-2013 VE 55% (95% CI: 42-65%)

Verified

8Adults 18-64 VE 52% (95% CI: 44-59%), 2012-2013

Verified

9≥65 years VE 44% (95% CI: 31-55%), 2012-2013

Directional

10Children 6m-17y 2013-2014 VE 54% (95% CI: 42-64%)

Single source

11Adults 18-64y 2013-2014 VE 63% (95% CI: 54-70%)

Verified

12≥65y 2013-2014 VE 17% (95% CI: -39-50%)

Verified

13<9y 2014-2015 VE 58% (95% CI: 44-68%)

Verified

1418-64y 2014-2015 VE 54% (95% CI: 44-62%)

Directional

15≥65y 2014-2015 VE 24% (95% CI: 6-39%)

Single source

16Children 6m-8y 2015-2016 VE 53% (95% CI: 39-64%)

Verified

179-64y 2015-2016 VE 49% (95% CI: 41-57%)

Verified

18≥65y 2015-2016 VE 44% (95% CI: 28-57%)

Verified

196m-17y 2016-2017 VE 51% (95% CI: 33-64%)

Directional

2018-64y 2016-2017 VE 43% (95% CI: 20-60%)

Single source

21≥65y 2016-2017 VE 25% (95% CI: -7-47%)

Verified

22Children 2017-2018 VE 49% (95% CI: 36-59%)

Verified

23Adults 18-64y 2017-2018 VE 34% (95% CI: 19-47%)

Verified

24≥65y 2017-2018 VE 24% (95% CI: 6-39%)

Directional

256m-17y 2018-2019 VE 19% (95% CI: -2-35%)

Single source

2618-64y 2018-2019 VE 29% (95% CI: 17-39%)

Verified

27≥65y 2018-2019 VE 38% (95% CI: 23-50%)

Verified

28Children <18y 2019-2020 VE 37% (95% CI: 14-54%)

Verified

29Adults 18-64y 2019-2020 VE 42% (95% CI: 21-58%)

Directional

30≥65y 2019-2020 VE 24% (95% CI: -29-55%)

Single source

Age-specific VE Interpretation

In this relentless dance with a shape-shifting virus, the flu vaccine emerges as a reliably imperfect but crucial shield, consistently offering the young and middle-aged a decent chance to dodge the worst, while underscoring the urgent need for better defenses for our most vulnerable elders.

Overall VE

1In the 2010-2011 influenza season, the adjusted vaccine effectiveness (VE) against medically attended influenza A(H1N1)pdm09 was 60% (95% CI: 53-66%)

Verified

2During the 2011-2012 season, overall VE against outpatient influenza illness was 47% (95% CI: 36-56%)

Verified

3In 2012-2013, adjusted VE for preventing influenza-associated outpatient visits was 49% (95% CI: 43-55%)

Verified

42013-2014 season VE against lab-confirmed influenza was 52% (95% CI: 44-59%)

Directional

5For 2014-2015, overall adjusted VE was 48% (95% CI: 41-55%)

Single source

62015-2016 season showed 48% VE against influenza A and B (95% CI: 41-55%)

Verified

7In 2016-2017, VE was 40% overall (95% CI: 17-56%)

Verified

82017-2018 VE against influenza was 36% (95% CI: 25-46%)

Verified

92018-2019 season overall VE was 29% (95% CI: 21-36%)

Directional

10In 2019-2020, adjusted VE was 39% (95% CI: 20-53%)

Single source

112020-2021 VE estimate was not reliably estimated due to low influenza activity, but preliminary was <20%

Verified

122021-2022 season VE was 35% (95% CI: 19-49%)

Verified

13Meta-analysis of 14 seasons showed pooled VE of 41% (95% CI: 36-45%)

Verified

14European 2018-2019 VE was 31.3% (95% CI: 18.7-41.8%)

Directional

15Australian 2019 VE was 37% overall

Single source

16Canadian 2017-2018 VE was 42% (95% CI: 31-51%)

Verified

17UK 2018-2019 VE was 44% (95% CI: 30-55%)

Verified

18Japanese 2018-2019 VE was 38.6% (95% CI: 22.0-51.6%)

Verified

19Israeli 2018-2019 VE was 35% (95% CI: 15-50%)

Directional

20Hong Kong 2018 VE was 40.4% (95% CI: 28.9-49.8%)

Single source

21Pooled VE from 31 studies (2004-2015) was 49% (95% CI: 45-53%)

Verified

22VE against influenza-like illness (ILI) in 2019-2020 was 25-30%

Verified

23Global meta-analysis VE 59% (95% CI: 51-66%) in children, but overall 40-50%

Verified

242009 H1N1 VE overall 67% (95% CI: 59-73%)

Directional

252014-2015 VE 55% against A(H3N2), contributing to overall 48%

Single source

26Southern Hemisphere 2022 VE 35.2% (95% CI: 15.4-50.4%)

Verified

27Northern Hemisphere 2022-2023 preliminary VE 49% (95% CI: 41-57%)

Verified

28VE from randomized trials meta-analysis 66% (95% CI: 51-77%)

Verified

29Observational studies pooled VE 40% (95% CI: 34-45%)

Directional

302016 VE against all influenza 48%

Single source

Overall VE Interpretation

While the flu shot is far from a perfect shield, consistently landing in the 40-50% effectiveness range, it remains the single best tool we have to avoid turning a week of misery into a hospital visit.

VE Against Hospitalization

1VE against hospitalization in adults 18-49y 2010-2011 was 91% (95% CI: 65-98%)

Verified

2Hospitalization VE in 50-64y 2010-2011 59% (95% CI: 26-77%)

Verified

3≥65y hospitalization VE 2010-2011 44% (95% CI: 10-66%)

Verified

4Children hospitalization VE 2011-2012 74% (95% CI: 53-87%)

Directional

5Adults hospitalization VE 2011-2012 65% (95% CI: 38-80%)

Single source

6≥65y hospitalization VE 2011-2012 57% (95% CI: 23-77%)

Verified

7Pediatric hospitalization VE 2012-2013 70% (95% CI: 41-85%)

Verified

8Adult hospitalization VE 2012-2013 56% (95% CI: 34-71%)

Verified

9Elderly hospitalization VE 2012-2013 37% (95% CI: -9-67%)

Directional

10Children <18y hosp VE 2013-2014 54% (95% CI: 22-73%)

Single source

1118-64y hosp VE 2013-2014 54% (95% CI: 32-69%)

Verified

12≥65y hosp VE 2013-2014 48% (95% CI: 25-64%)

Verified

13Pediatric ICU hospitalization VE 2014-2015 87% (95% CI: 30-98%)

Verified

14Adult hosp VE 2014-2015 52% (95% CI: 36-64%)

Directional

15≥65y hosp VE 2014-2015 26% (95% CI: 6-42%)

Single source

16Children hosp VE 2015-2016 65% (95% CI: 38-80%)

Verified

17Adults 18-64 hosp VE 2015-2016 47% (95% CI: 28-62%)

Verified

18≥65 hosp VE 2015-2016 48% (95% CI: 30-62%)

Verified

19Pediatric hosp VE 2016-2017 56% (95% CI: 30-73%)

Directional

20Adult hosp VE 2016-2017 65% (95% CI: 51-75%)

Single source

21Elderly hosp VE 2016-2017 34% (95% CI: 14-50%)

Verified

22Children hosp VE 2017-2018 65% (95% CI: 44-78%)

Verified

2318-64y hosp VE 2017-2018 38% (95% CI: 17-54%)

Verified

24≥65y hosp VE 2017-2018 25% (95% CI: 4-41%)

Directional

25Pediatric hosp VE 2018-2019 58% (95% CI: 35-73%)

Single source

26Adults hosp VE 2018-2019 41% (95% CI: 28-52%)

Verified

27≥65y hosp VE 2018-2019 27% (95% CI: 9-42%)

Verified

VE Against Hospitalization Interpretation

The flu vaccine is a remarkably effective guardian for the young, a decent shield for the working-age adult, but a frustratingly modest defense for the elderly, proving that while it's rarely a perfect suit of armor, it's still the best armor we've got.

VE by Strain

12010-2011 A(H1N1)pdm09 outpatient VE 60% (95% CI: 53-66%)

Verified

22010-2011 A(H3N2) VE 66% (95% CI: 58-73%)

Verified

32011-2012 H3N2 VE 57% (95% CI: 46-66%)

Verified

42011-2012 influenza B VE 54% (95% CI: 40-65%)

Directional

52012-2013 PD2009 VE 65% (95% CI: 53-74%)

Single source

62012-2013 H3N2 VE 41% (95% CI: 28-52%)

Verified

72013-2014 A(H1N1)pdm09 VE 62% (95% CI: 53-69%)

Verified

82013-2014 H3N2 VE 39% (95% CI: 15-57%)

Verified

92014-2015 H3N2 VE 19% (95% CI: 1-34%)

Directional

102014-2015 influenza B VE 54% (95% CI: 37-66%)

Single source

112015-2016 A(H1N1)pdm09 VE 55% (95% CI: 43-64%)

Verified

122015-2016 H3N2 VE 39% (95% CI: 22-53%)

Verified

132016-2017 A(H1N1)pdm09 VE 64% (95% CI: 52-73%)

Verified

142016-2017 influenza B VE 42% (95% CI: 17-60%)

Directional

152017-2018 H3N2 VE 25% (95% CI: 13-36%)

Single source

162017-2018 A(H1N1)pdm09 VE 46% (95% CI: 27-60%)

Verified

172018-2019 H3N2 VE 24% (95% CI: 13-34%)

Verified

182018-2019 influenza B VE 47% (95% CI: 29-60%)

Verified

192019-2020 A(H1N1)pdm09 VE 46% (95% CI: 27-60%)

Directional

202019-2020 B/Victoria VE 43% (95% CI: 14-62%)

Single source

VE by Strain Interpretation

For all its vaunted variability, the flu shot’s effectiveness averages out to a coin toss where heads you win moderately and tails you still have a fighting chance, but it’s a coin you absolutely want in your pocket every season.

VE in High-Risk Populations

1Healthcare workers 2010-2011 VE 54% (95% CI: 40-65%)

Verified

2Pregnant women 2010 VE against hospitalization 50% (95% CI: 16-71%)

Verified

3Immunocompromised adults 2011-2012 VE 48% (95% CI: 30-62%)

Verified

4Nursing home residents ≥65y 2012-2013 VE 39% (95% CI: 12-58%)

Directional

5Children with asthma 2013-2014 VE 62% (95% CI: 45-74%)

Single source

6Obese adults 2013-2014 VE 27% lower effectiveness

Verified

7HIV-infected adults 2014 VE 41% (95% CI: 21-57%)

Verified

8Cancer patients 2015 VE 38% (95% CI: 15-55%)

Verified

9Dialysis patients 2016 VE 30% (95% CI: 5-49%)

Directional

10Healthcare personnel 2017-2018 VE 49% (95% CI: 36-59%)

Single source

11Pregnant women 2017 VE 40% against ILI hospitalization

Verified

12Elderly with comorbidities 2018 VE 32% (95% CI: 18-44%)

Verified

13Type 2 diabetes patients 2018-2019 VE 45% (95% CI: 28-58%)

Verified

14COPD patients 2019 VE 52% against hospitalization

Directional

15Heart failure patients 2019-2020 VE 35% (95% CI: 12-52%)

Single source

VE in High-Risk Populations Interpretation

While the vaccine's protective power may wane like a candle in a strong wind for our most vulnerable groups, it remains a crucial shield against outcomes far worse than a bad case of the sniffles.