Think of the flu shot as a suit of armor that's only partially effective, yet wearing it still prevented an estimated 100,000 hospitalizations last season alone.
Key Takeaways
- In the 2022-2023 influenza season, the flu vaccine effectiveness against hospitalization was estimated at 46% overall for adults aged 18 years and older in the United States
- The 2021-2022 flu vaccine was 35% effective in preventing influenza-associated outpatient visits among children aged 6 months to 17 years, based on CDC surveillance data
- Flu vaccination reduced the risk of influenza-related hospitalization by 40% in pregnant women during the 2019-2020 season, per CDC analysis
- Only 1.4% of people reported severe allergic reactions to flu shots from 2010-2020 VAERS data
- Guillain-Barré Syndrome risk after flu vaccine is about 1-2 additional cases per million doses, lower than flu illness risk
- No increased risk of miscarriage from flu vaccine in first trimester, per 2021 meta-analysis of 2 million pregnancies
- Flu vaccination coverage among healthcare personnel reached 83% in 2019-2020 US
- US adult flu vaccination rate 52.9% for 2022-2023 season, per NHIS survey
- Children 6m-17y flu vac coverage 57.9% in 2022-2023, CDC data
- Flu vaccination prevented an estimated 7.5 million illnesses, 3.5 million medical visits, 100,000 hospitalizations, and 7,000 deaths in 2022-2023 US season
- From 2010-2020, flu vaccines prevented 13 million illnesses and 110,000 deaths in US
- Flu shots averted 4.4 million cases and saved $1.2 billion healthcare costs in 2019-2020 US
- Flu vac recommended annually for everyone 6 months and older by CDC ACIP
- High-dose or adjuvanted vaccines preferred for 65+ adults per 2022 ACIP
- Pregnant women should receive inactivated flu vaccine any trimester, WHO/ACIP
Flu shots vary in effectiveness but consistently reduce serious risks across all age groups.
Coverage
- Flu vaccination coverage among healthcare personnel reached 83% in 2019-2020 US
- US adult flu vaccination rate 52.9% for 2022-2023 season, per NHIS survey
- Children 6m-17y flu vac coverage 57.9% in 2022-2023, CDC data
- Pregnant women US flu vac rate 49.3% in 2021-2022
- Seniors 65+ coverage 74.2% in 2022-2023, highest group
- Global flu vac coverage <10% in low-income countries 2022 WHO estimate
- US HCP vac rate 91.7% in 2022-2023
- School-aged children coverage increased 5% from 2019 to 2023
- Medicaid enrollees flu vac 47% in 2021-2022
- Rural US adults flu vac 45.2% vs 54.1% urban 2022
- Hispanic adults coverage 43.1% in 2022-2023, lower than non-Hispanic white 56.2%
- Employer-mandated vac led to 96% HCP coverage in hospitals 2020
- WHO target 75% seniors coverage by 2030, current EU avg 47%
- US college students flu vac 41.3% in 2022 NIS
- Black non-Hispanic adults 44.4% coverage 2022-2023
- Asia-Pacific flu vac coverage avg 25% in 2022
- Nursing home residents 85% vaccinated 2022 CMS data
- Teachers coverage 48% in US schools 2022
- Low-income countries <5% pregnant women vaccinated 2023 GAVI report
- US veterans 72% flu vac rate 2022 VA data
- First Nations Canada flu vac 52% vs 38% general pop 2022
- Pharmacist-administered shots boosted coverage by 10% in 2019 study
- UK flu vac uptake 75.3% over-65s 2022-2023
- Australia 2022 flu vac coverage 35% adults
- US 6m-4y children coverage 64.6% 2022-2023
- Global pediatric coverage <20% outside high-income countries 2023
Coverage Interpretation
The data reveals a stark and somewhat predictable hierarchy of flu shot adoption: healthcare workers, who see the consequences firsthand, lead the charge at over 90%, while the general adult population lingers around a coin-flip's chance of 53%, proving that nothing motivates like professional proximity to suffering.
Efficacy
- In the 2022-2023 influenza season, the flu vaccine effectiveness against hospitalization was estimated at 46% overall for adults aged 18 years and older in the United States
- The 2021-2022 flu vaccine was 35% effective in preventing influenza-associated outpatient visits among children aged 6 months to 17 years, based on CDC surveillance data
- Flu vaccination reduced the risk of influenza-related hospitalization by 40% in pregnant women during the 2019-2020 season, per CDC analysis
- In older adults (65+), the high-dose flu vaccine showed 24% greater relative efficacy against flu-related hospitalization compared to standard-dose vaccine in a 2020-2021 study
- The adjuvanted flu vaccine demonstrated 51% vaccine effectiveness against laboratory-confirmed influenza hospitalization in adults 65+ during 2019-2020
- Flu vaccine effectiveness was 54% against H1N1pdm09 outpatient illness in children during 2022-2023, according to CDC VISION network
- Recombinant quadrivalent flu vaccine reduced medically attended influenza by 12% more than standard egg-based vaccine in working-age adults, per 2018-2019 trial
- In the 2018-2019 season, flu vaccine was 29% effective against influenza A(H3N2) hospitalization in adults
- Live attenuated influenza vaccine (LAIV) was 54.4% effective against influenza illness in children 2-17 years during 2016-2017
- Cell-culture based flu vaccine showed 88.9% efficacy against culture-confirmed influenza in children 2-17 years in 2017-2018 RCTs
- Flu vaccine reduced ICU admissions by 82% in vaccinated vs unvaccinated during 2010-2011 season in Canada
- In Europe, 2018-2019 flu vaccine effectiveness was 31% against GP consultations for influenza-like illness, per I-MOVE network
- Quadrivalent flu vaccine efficacy was 70.2% against any influenza strain in children 6-35 months in pivotal trial
- High-dose trivalent flu vaccine had 24% relative efficacy vs standard dose in preventing flu in 60+ adults
- Flu shot effectiveness against pandemic H1N1 was 68% in healthcare workers during 2009
- In 2020-2021, despite low flu circulation, modeling estimated 39% VE against hospitalization
- Australian 2022 flu season VE was 44% against hospitalization overall
- Nasal spray flu vaccine efficacy 45.7% vs trivalent inactivated in kids 2-15 years
- Flu vaccine VE 59% against ED visits in HMO populations 2013-2014
- In Japan, 2018-2019 inactivated flu vaccine VE 38.6% against influenza A(H1N1)
- Fluzone High-Dose VE 51% vs standard dose hospitalization prevention in seniors
- UK 2019-2020 live vaccine VE 57% in schoolchildren 2-17 years
- Flu vaccine 48% effective against lab-confirmed flu hospitalization in under-65s 2022-2023
- Adjuvanted vaccine VE 32% against any flu hospitalization in 65+ during low severity season
- Pediatric flu VE 54% against outpatient acute respiratory illness 2022-2023
- Flu vaccination associated with 26% lower risk of cardiac events post-flu infection
- VE 67% against H3N2 in adults 18-49 years 2019-2020
- In 2017-2018, egg-grown vaccine VE lower by 14.8% vs cell-based due to mismatch
- Flu shot reduced absenteeism by 28% in vaccinated workers 2010 study
- Maternal flu vaccination 70% effective in protecting infants <6 months
Efficacy Interpretation
It’s not a magic shield, but wearing half a suit of armor in a knife fight is still vastly preferable to going shirtless.
Public Health Impact
- Flu vaccination prevented an estimated 7.5 million illnesses, 3.5 million medical visits, 100,000 hospitalizations, and 7,000 deaths in 2022-2023 US season
- From 2010-2020, flu vaccines prevented 13 million illnesses and 110,000 deaths in US
- Flu shots averted 4.4 million cases and saved $1.2 billion healthcare costs in 2019-2020 US
- Vaccination reduced flu mortality by 50% in seniors during 2012-2013 high severity season
- Global flu vaccines prevent 1-2 million respiratory deaths annually WHO estimate
- In 2018-2019, vac reduced pediatric deaths by 37% vs unvaccinated
- Flu vac associated with 65% lower all-cause mortality in nursing homes 2021
- Prevented 1 million hospitalizations 2005-2014 cumulative US CDC model
- Reduced school absenteeism by 3.5 days per 100 students during peak flu weeks
- Flu vac lowered cardiovascular hospitalization risk by 18% in heart failure patients
- Averted 800,000 GP visits in England 2022-2023 flu season
- Vaccination cut ICU admissions 75% in vaccinated asthmatics 2018 study
- Reduced excess mortality by 40% in Europe 2016-2017 per ECDC
- Flu shots saved 52,000 lives in US 2010-2020 decade
- Lowered antibiotic prescriptions by 25% in vaccinated children 2019 trial
- Prevented 2.4 million cases in Australia 2018-2022 cumulative
- Reduced frailty progression by 27% in vaccinated seniors 2020 cohort
- Averted $3.8 billion economic loss from flu in 2022-2023 US season
- Flu vac decreased COPD exacerbations by 30% in 2021 meta-analysis
- Protected 70% of infants from hospitalization via maternal vac 2019-2020
- Reduced workplace productivity loss by 40% in vaccinated employees
- Lowered secondary bacterial pneumonia by 50% post-flu vac
- Averted 300 pediatric deaths annually avg US 2010-2020
- Decreased emergency visits by 27% in vaccinated 5-17y during 2017-2018
Public Health Impact Interpretation
The flu shot is like a tiny superhero: it prevents millions of illnesses and saves billions of dollars, proving that a simple jab is one of the most powerful tools we have for public health.
Recommendations
- Flu vac recommended annually for everyone 6 months and older by CDC ACIP
- High-dose or adjuvanted vaccines preferred for 65+ adults per 2022 ACIP
- Pregnant women should receive inactivated flu vaccine any trimester, WHO/ACIP
- Children 6m-8y need 2 doses first time if no prior vac, CDC guideline
- Healthcare workers prioritization group 1 for annual flu vac
- Egg-allergic persons can receive any licensed flu vaccine, ACIP 2016 update
- Universal recommendation since 2010 for all 6m+, reaffirmed 2023
- Live attenuated vaccine for 2-49y healthy non-pregnant, FDA approved
- Caregivers of infants <6m urged to vaccinate, CDC
- Annual revaccination necessary due to antigenic drift, WHO
- Recombinant vaccine option for egg-allergic, ACIP endorsed
- Timing: September-October optimal, but anytime during season, CDC
- Immunocompromised should get inactivated vaccine, avoid LAIV
- Household contacts of high-risk vaccinate regardless of health
- Medicare covers flu shots annually no copay, CMS policy
- School requirements in 40+ US states for flu vac in some cases
- Combination flu-COVID vaccine under study, but separate recommended now
- Travelers to tropics or southern hemisphere vaccinate per schedule, CDC
- Poultry workers get 2 doses H5N1 vaccine if exposed, special rec
- Asylum seekers/immigrants screening includes flu vac catch-up, USPHS
- Diabetes patients annual flu vac strongly advised, ADA/ACIP
- Postpartum women vaccinate within 14 days discharge
- Heart disease patients vac reduces hospitalization 36%, AHA rec
- Best by mid-October for max protection, extend if low coverage
Recommendations Interpretation
The CDC's flu shot guidelines are a masterclass in universal common sense, targeting everyone from six-month-olds to seniors with surgical precision, because protecting the herd requires vaccinating every last sheep—and the shepherd, the shepherd's pregnant wife, their egg-allergic uncle, their cardiologist, and even the guy who works with the chickens.
Safety
- Only 1.4% of people reported severe allergic reactions to flu shots from 2010-2020 VAERS data
- Guillain-Barré Syndrome risk after flu vaccine is about 1-2 additional cases per million doses, lower than flu illness risk
- No increased risk of miscarriage from flu vaccine in first trimester, per 2021 meta-analysis of 2 million pregnancies
- Local reactions like soreness at injection site occur in up to 25% of recipients, resolving in 1-2 days
- Anaphylaxis post-flu vaccine incidence 1.35 per million doses from 2009-2019
- No association between flu vaccine and Bell's palsy in large cohort studies
- Fever after flu shot in children <10% incidence, usually mild and short-lived
- 1976 swine flu vaccine linked to 1 extra GBS case per 100,000, modern vaccines much safer
- No causal link between flu vaccine and autism, confirmed by multiple studies including Danish cohort of 657,461 children
- Myocarditis risk from flu vaccine negligible, <1 per million, vs 10x higher from flu infection
- Flu shot does not cause flu, as inactivated vaccines contain dead virus
- Post-vaccination fatigue in 10-15% of adults, lasts <24 hours typically
- No increased risk of dementia from flu vaccines in seniors, per UK study of 7 million doses
- Egg allergy no contraindication for most flu vaccines since 2013, per ACIP
- Live attenuated flu vaccine safe for healthy non-pregnant 2-49 year olds, no transmission to contacts
- VAERS reported 0.0001% serious adverse events post-flu shot 2019-2020
- No link to multiple sclerosis exacerbation from flu vaccine, per systematic review
- Headache post-vaccination in 16% of recipients, mild and self-limiting
- Flu vaccine safe in HIV patients, no increased progression
- Arm pain/swelling in 5-10% children, no long-term effects
- No association with narcolepsy except 2009 AS03-adjuvanted vaccine in Sweden/Finland
- Post-flu shot syncope rare, 7.5 per 100,000 doses, preventable by observation
- Safe for cancer patients, improves survival odds vs no vaccination
- No infertility risk from flu vaccine, debunked by reproductive health studies
- Muscle aches in 10% adults post-shot, comparable to placebo
Safety Interpretation
The flu shot’s greatest risk is the temptation to scroll through its overwhelmingly reassuring safety statistics on your phone until your arm gets sore from holding it up.
Sources & References
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