The effectiveness of the flu shot is always a hot topic in the Fall and Winter months.

If you’re joining us for the first time, welcome!  This article is part 3 of our series: The Flip Side of the Flu Shot It’s a work-in-progress whereby I’m answering questions for my health and wellness tribe because there is so much confusion and controversy around the flu shot.  I am compiling “the other side of the coin” resources for everyone to review.

Past and upcoming posts:

The (In) Effectiveness of the Flu Shot

The following is an ongoing list of studies that share the ineffectiveness of the flu shot.  As we reviewed in our discussion about Flu shot marketing, we are typically only hearing one side of the story.  We’re typically reading about all of the reasons we should get the flu shot with scary statistics and news reports with pictures of really sick people.

This shouldn’t come to your surprise but it should inspire you to ask a great question: If the flu shot is ineffective, why are we still producing it? Why are we still taking it?

Some argue that f you’re vaccinated and you do get the flu, your symptoms will be much less severe and the length of time you’re ill will shortened as well. If you read ahead in our series; however, you may read about other ways to prevent and reduce the severity and duration of symptoms without needing the shot at all, with even greater effectiveness.


Influenza vaccination and risk of community-acquired pneumonia in immunocompetent elderly people: a population-based, nested case-control study.

This study concluded: “Influenza vaccination was not associated with a reduced risk of community-acquired pneumonia (odds ratio 0.92, 95% CI 0.77-1.10) during the influenza season.”https://www.ncbi.nlm.nih.gov/pubmed/18675690


Effectiveness of inactivated influenza vaccines varied substantially with antigenic match from the 2004-2005 season to the 2006-2007 season. http://www.ncbi.nlm.nih.gov/pubmed/19086915 
Belongia EA, et al. J Infect Dis. 2009 Jan 15;199(2):159-67.PMID: 19086915.

Results:
Influenza was detected in 167 (20%) of 818 patients in 2004-2005, in 51 (14%) of 356 in 2005-2006, and in 102 (11%) of 932 in 2006-2007. Analyses that used data from test-negative control subjects showed that vaccine effectiveness was 10% (95% confidence interval [CI], -36% to 40%) in 2004-2005, 21% (95% CI, -52% to 59%) in 2005-2006, and 52% (95% CI, 22% to 70%) in 2006-2007. Using data from traditional control subjects, effectiveness for those seasons was estimated to be 5% (95% CI, -52% to 40%), 11% (95% CI, -96% to 59%), and 37% (95% CI, -10% to 64%), respectively; confidence intervals included 0. The percentage of viruses that were antigenically matched to vaccine strains was 5% (3 of 62) in 2004-2005, 5% (2 of 42) in 2005-2006, and 91% (85 of 93) in 2006-2007.


Children
http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2805%2917984-7/fulltext

Results
“Inactivated vaccines had lower efficacy (65%) than live attenuated vaccines, and in children aged 2 years or younger they had similar effects to placebo.” “If influenza immunisation in children is to be recommended as public-health policy, large-scale studies assessing such important outcomes and undertaking direct comparisons of vaccines are urgently needed.”


Effectiveness of the 2003-2004 influenza vaccine among children 6 months to 8 years of age, with 1 vs 2 doses. Ritzwoller DP, et al. Pediatrics. 2005 Jul;116(1):153-9. http://www.ncbi.nlm.nih.gov/pubmed/15995046

Results

For fully vaccinated children 6 to 23 months of age, vaccine effectiveness against influenza-like illness and pneumonia and influenza was 25% and 49%, respectively. No statistically significant reduction in influenza-like illness or pneumonia and influenza rates was observed for partially vaccinated children 6 to 23 months of age (-3% and 22%, respectively). For fully vaccinated children 6 months to 8 years of age, vaccine effectiveness against influenza-like illness and pneumonia and influenza was 23% and 51%, respectively. For partial vaccination, vaccine effectiveness was significant only for pneumonia and influenza (23%).



Effectiveness of influenza vaccine during pregnancy in preventing hospitalizations and outpatient visits for respiratory illness in pregnant women and their infants.
Black SB, et al. Am J Perinatol. 2004 Aug;21(6):333-9. PMID: 15311370
http://www.ncbi.nlm.nih.gov/pubmed/15311370

Conclusion
Although the immunogenicity of influenza vaccination in pregnancy in mother and infant has been well documented, in this study, we were unable to demonstrate the effectiveness of influenza vaccination with data for hospital admissions and physician visits.


Effectiveness of trivalent inactivated influenza vaccine in influenza-related hospitalization in children: A case-control study. Authors: Joshi, Avni Y et al,  Allergy and Asthma Proceedings, Volume 33, Number 2, March/April 2012 , pp. e23-e27(5).http://www.ingentaconnect.com/content/ocean/aap/2012/00000033/00000002/art00003?token=004c18a26994051d573d257025702c23792f7c4038762c3a797c4e75477e4324576b642738cd

Conclusion
TIV did not provide any protection against hospitalization in pediatric subjects, especially children with asthma. On the contrary, we found a threefold increased risk of hospitalization in subjects who did get the TIV vaccine. This may be a reflection not only of vaccine effectiveness but also the population of children who are more likely to get the vaccine.


Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis.
Osterholm MT et al. Lancet Infect Dis. 2012 Jan;12(1):36-44.PMID: 22032844
Study Type : Meta Analysis http://www.ncbi.nlm.nih.gov/pubmed/22032844 

Conclusion
There is a lack of evidence for the effectiveness of influenza vaccines in adults aged 65 years or older.


Evidence of bias in estimates of influenza vaccine effectiveness in seniors
Lisa A Jackson et al. Int. J. Epidemiol. (April 2006) 35 (2): 337-344.
http://ije.oxfordjournals.org/content/35/2/337

Conclusion
Numerous observational studies have reported that seniors who receive influenza vaccine are at substantially lower risk of death and hospitalization during the influenza season than unvaccinated seniors. These estimates could be influenced by differences in underlying health status between the vaccinated and unvaccinated groups. Since a protective effect of vaccination should be specific to influenza season, evaluation of non-influenza periods could indicate the possible contribution of bias to the estimates observed during influenza season.

The reductions in risk before influenza season indicate preferential receipt of vaccine by relatively healthy seniors. Adjustment for diagnosis code variables did not control for this bias. In this study, the magnitude of the bias demonstrated by the associations before the influenza season was sufficient to account entirely for the associations observed during influenza season.


Further Evidence for Bias in Observational Studies of Influenza Vaccine Effectiveness: The 2009 Influenza A(H1N1) Pandemic
Michael L. Jackson et al. Am. J. Epidemiol. (2013)
http://aje.oxfordjournals.org/content/early/2013/08/23/aje.kwt124.abstract

Conclusion
In a year with minimal seasonal influenza, we found no evidence that confounding in autumn preinfluenza periods is qualitatively different from confounding in winter. This supports the use of preinfluenza periods as control time periods in studies of influenza vaccine effectiveness.


Impact of influenza vaccination on seasonal mortality in the US elderly population.
Simonsen L et al. Arch Intern Med. 2005 Feb 14;165(3):265-72. PMID: 15710788.
Study Type : Human Study
http://www.ncbi.nlm.nih.gov/pubmed/15710788

Conclusion
Widening influenza vaccine coverage is not correlated with declining mortality rates in any age group. The benefits of vaccination are substantially overestimated.


Impact of maternal influenza vaccination during pregnancy on the incidence of acute respiratory illness visits among infants.
France EK, et al.  Arch Pediatr Adolesc Med. 2006 Dec;160(12):1277-83. http://www.ncbi.nlm.nih.gov/pubmed/17146026

Conclusion
Maternal influenza vaccination did not reduce visit rates during any of the 4 time periods (IRR for peak influenza season, 0.96; 95% confidence interval, 0.86-1.07) and did not delay the onset of first respiratory illness. We were unable to demonstrate that maternal influenza vaccination reduces respiratory illness visit rates among their infants.


Influenza Vaccination During Pregnancy: A Critical Assessment of the Recommendations of the Advisory Committee on Immunization Practices (ACIP)
David M. Ayoub, M.D., F. Edward Yazbak, M.D, Journal of American Physicians and Surgeons Volume 11 Number 2 Summer 2006
http://www.jpands.org/vol11no2/ayoub.pdf

Conclusion
There was no statistically significant difference in illness rates among the vaccinated and unvaccinated women (4.5/10,000 vs. 4.4/10,000) or their offspring. Vaccination also had no impact on illness rates among women with asthma (3.7/10,000 vs. 4.1/10,000), a subgroup the CDC has consistently claimed to be at high risk for influenza complications.


Influenza vaccination for healthcare workers who work with the elderly. Thomas RE et al. Cochrane Database Syst Rev. 2010(2):CD005187. PMID:20166073. Study Type : Meta Analysis
http://www.ncbi.nlm.nih.gov/pubmed/20166073

Conclusion
Influenza vaccination for healthcare workers who work with the elderly has no effect on laboratory-proven influenza, pneumonia or deaths from pneumonia.


Influenza vaccination for healthcare workers who work with the elderly.
Thomas RE et al. Cochrane Database Syst Rev. 2006 ;3:CD005187. Epub 2006 Jul 19. PMID:16856082. Study Type : Meta Analysis
http://www.ncbi.nlm.nih.gov/pubmed/16856082

Conclusion
We concluded that there is no credible evidence that vaccination of healthy people under the age of 60, who are healthcare workers caring for the elderly, affects influenza complications in those cared for.


Influenza vaccine effectiveness among children 6 to 59 months of age during 2 influenza seasons: a case-cohort study. Szilagyi PG,et al. Arch Pediatr Adolesc Med. 2008 Oct;162(10):943-51. New Vaccine Surveillance Network. Strong Memorial Hospital, Rochester, NY 14642, USA.
http://www.ncbi.nlm.nih.gov/pubmed/18838647

Conclusion
In 2 seasons with suboptimal antigenic match between vaccines and circulating strains, we could not demonstrate vaccine effectiveness in preventing influenza-related inpatient/ED or outpatient visits in children younger than 5 years. Further study is needed during years with good vaccine match.
Plain Language: Influenza vaccines were not shown to be effective among children 6 to 59 months of age during 2 influenza seasons.


Influenza Vaccine: Review of Effectiveness of the U.S. Immunization Program, and Policy Considerations
David A. Geier, B.A., et al. Journal of American Physicians and Surgeons Volume 11 Number 3 Fall 2006. Association of American Physicians and Surgeons, Inc.
http://www.ids-healthcare.com/Common/Paper/Paper_172/Influenza%20Vaccine.pdf

Conclusion
Between 1979 and 2000, influenza vaccine was shown to have little or no effectiveness over the U.S. population for preventing influenza cases, deaths, or hospital admissions. Influenza vaccination was correlated with a decreased number of deaths, but this correlation (of approximately 6.2%) was not statistically significant. For the other two measures, there were nonsignificant correlations between increasing influenza vaccination coverage and increasing numbers of influenza cases (0.6%) and influenza hospital discharge diagnoses (4.8%).

The annual risk of influenza is substantial, affecting, on average, about 37.6% of the population annually. However, these millions of influenza cases annually translate into an average of about 1,300 deaths in the U.S., not the often-quoted inflated number of 36,000 influenza deaths per year.

The current influenza vaccine program seems to be ineffective, and the U.S. should consider replacing it with a program based primarily on antiviral medications. Research is needed to develop more and better antivirals, especially agents to which influenza viruses do not readily develop resistance.

If the influenza vaccine program is to continue, improved vaccines, which are not potentially infectious, are needed. It will be necessary to develop and license an effective vaccine that confers significant immunity to a wide variety of strains so that vaccine does not have to be given every year.

Vaccine recipients need to be informed of the limitations and risks of the vaccine and of the alternatives to vaccination. In particular, they need to know of the possibility that repeated vaccinations may increase the risk of adverse effects.


Influenza-related mortality in the Italian elderly: no decline associated with increasing vaccination coverage. Rizzo C et al. Vaccine. 2006 Oct 30;24(42-43):6468-75. PMID: 16876293. Study Type : Human Study
http://www.ncbi.nlm.nih.gov/pubmed/16876293

Conclusion
Influenza-related mortality is not prevented with increasing vaccination coverage.


Interim within-season estimate of the effectiveness of trivalent inactivated influenza vaccine–Marshfield, Wisconsin, 2007-08 influenza season.
Centers for Disease Control and Prevention (CDC). MMWR Morb Mortal Wkly Rep. 2008 Apr 18;57(15):393-8. PMID: 18418344
http://www.ncbi.nlm.nih.gov/pubmed/18418344

This report summarizes interim results of a 2008 case-control study to estimate the effectiveness of trivalent inactivated influenza vaccine for prevention of medically attended, laboratory-confirmed influenza during the 2007-08 influenza season, when most circulating influenza A (H3N2) and B viruses were suboptimally matched to the vaccine strains. Despite the suboptimal match between two of three vaccine strains and circulating influenza strains, overall VE in the study population during January 21-February 8, 2008, was 44%. These findings demonstrate that, in any season, assessment of the clinical effectiveness of influenza vaccines cannot be determined solely by laboratory evaluation of the degree of antigenic match between vaccine and circulation strains.’


No effect of 2008/09 seasonal influenza vaccination on the risk of pandemic H1N1 2009 influenza infection in England. Pebody R, et al.  Vaccine. 2011 Jan 31. Epub 2011 Jan 31. PMID: 21292008
Study Type : Meta Analysis
http://www.ncbi.nlm.nih.gov/pubmed/21292008

The effectiveness of the 2008-2009 seasonal flu vaccine in England was -6%. There was no evidence prior vaccination with trivalent influenza vaccine significantly altered subsequent risk of pandemic influenza H1N1 2009 infection.


Vaccines for preventing influenza in healthy adults
Tom Jefferson et al, 2010, DOI: 10.1002/14651858.CD001269.pub4
http://onlinelibrary.wiley.com/doi/10.1002/14651858.CD001269.pub4/full#CD001269-bbs2-0169

“30% of unvaccinated people versus 24% of people vaccinated with inactivated parenteral vaccines developed symptoms of influenza-like-illness.”

“70% of the unvaccinated study participants did not get influenza-like-illness symptoms, compared to 76% of the vaccinated study participants, vaccinated with inactivated parenteral vaccines.”

= the vaccine offered a level of protection just 6% above those with no vaccination

“When the vaccine matched the viral circulating strain and circulation was high, 4% (2% to 5%) of unvaccinated people versus 1% of vaccinated people developed influenza symptoms (efficacy). When the vaccine content did not match the circulating influenza viruses 1% of vaccinated people developed symptoms compared to 2% of unvaccinated people.”


Vaccines for preventing influenza in healthy children.
Jefferson T et al. Altern Ther Health Med. 2009 Sep-Oct;15(5):44-6. PMID: 18425905.
Study Type : Meta Analysis
http://www.ncbi.nlm.nih.gov/pubmed/18425905

Inactivated flu vaccines have not been proven to be effective or safe in preventing influenza in healthy children under two.


Vaccines for preventing influenza in people with cystic fibrosis.
Dharmaraj P et al. Cochrane Database Syst Rev. 2009 Oct 7;(4):CD001753. PMID: 19821281
ArtiStudy Type : Meta Analysis
http://www.ncbi.nlm.nih.gov/pubmed/19821281

There is currently no evidence from randomised studies that influenza vaccine given to people with cystic fibrosis is of benefit to them.


Vaccines for preventing influenza in the elderly.
Jefferson T et al. Cochrane Database Syst Rev. 2010(2):CD004876. Epub 2010 Feb 17. PMID:20166072. Study Type : Meta Analysis
http://www.ncbi.nlm.nih.gov/pubmed/20166072

There is no solid evidence available supporting the belief that vaccines are effective in preventing influenza in the elderly.


What, in Fact, Is the Evidence That Vaccinating Healthcare Workers against Seasonal Influenza Protects Their Patients? A Critical Review
Zvi Howard Abramson et al, Int J Family Med. 2012; 2012: 205464.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3502850/

Conclusion
The arguments for uniform healthcare worker influenza vaccination are not supported by existing literature. The decision whether to get vaccinated should, except possibly in extreme situations, be that of the individual healthcare worker, without legal, institutional, or peer coercion.


Other flu shot studies (note: at the time of this post, I have yet to cross-reference for duplicate studies):


Best in health,

Trish

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