Influenza Vaccination - Is It Worth The Risk?
By F. Edward Yazbak , MD , FAAP

“We could not correlate increasing vaccination coverage after 1980 with declining mortality rates in any age group. Because fewer than 10% of all winter deaths were attributable to influenza in any season, we conclude that observational studies substantially overestimate vaccination benefit.”

So ends the abstract of a major report by the National Institute of Allergy and Infectious Diseases (NIAID) of the U.S. National Institutes of Health.

The results of the comprehensive study, undertaken by Lone Simonsen, Ph.D., a senior epidemiologist at the Institute (and others) were published in the Archives of Internal Medicine in February 2005 under the title “ Impact of influenza vaccination on seasonal mortality in the US elderly population”. (1)

Intrigued by the fact that the number of influenza-related deaths among the elderly kept increasing while the flu vaccination rates were also steadily rising (from about 20% in 1980 to around 65% in 2001), Simonsen and her team carefully and methodically estimated influenza-related and all deaths among the elderly during THIRTY THREE consecutive U.S. flu seasons (1968 to 2001) .

The authors noted:

  • That among those 85 years and older, the mortality rate did not change throughout the 33 influenza seasons
  • That among those 65 to 74 years of age, the mortality rate remained the same since 1980
  • And that t he “flu-related mortality” among the elderly always remained less than 10 percent of the total number of winter deaths.

In an interview, Dr. Simonsen said that the substantial increase in vaccination coverage should have led to a dramatic drop in flu deaths. "This is not what we found," she said. "Certainly if this intervention really does reduce winter deaths in the elderly by 50% we would expect to see it. So the mortality benefits are probably very much overestimated."

Dr. Simonsen then commented on the 1997-1998 flu season. The strains included in that season's vaccine were totally different from those cultured in the fifty states and therefore the vaccination of over 60% of eligible elderly did not actually protect them. Yet there were approximately 5,000 fewer excess deaths in this age group than there were the following flu season, when the same percentage of people were vaccinated with the correct strains. (2)

As a peace offering to the Centers for Disease Control and Prevention (CDC), Simonsen said that her findings suggested that a shift in strategy was indicated and that emphasis should be placed on vaccinating children who spread the flu virus around. She suggested that if 70 percent of schoolchildren were vaccinated, the elderly would be protected without the need for flu shots.

All what was needed was to convince parents to have their children vaccinated, in order to protect some unknown old people whose vaccinations were useless.

Until then parents had been far from “convinced”. In fact, during the fall of 2004:

  • Less than 30% of children at high risk received the flu vaccine
  • Only half of the high-risk children vaccinated during the previous season (2003-2004) were revaccinated
  • Almost 40% of parents of “unvaccinated older children in the high risk category” were still unconvinced that influenza vaccination was necessary. (3)

All that, in spite of a major and very costly publicity campaign that had surrounded the Spring 2004 launching of a new recommendation by the Advisory Committee on Immunization Practices (ACIP) of the CDC to not only vaccinate children in the high

risk groups but to also vaccinate ALL CHILDREN between the ages of 6 to 23-months against influenza - every year . (4)

The ACIP claimed that vaccinating young infants would protect them and would decrease hospital admissions for influenza-related illnesses and complications.

Luckily this time, it did not take thirty three years to know whether the vaccine was effective or not.

In an extensive review published in the Feb. 25, 2005 issue of The Lancet, Jefferson et al literally analyzed every available reference in any language that they could find in the Cochrane Library, MEDLINE, EMBASE Biological Abstracts and Science Citation Index to June 2004. Their review included 14 randomized controlled trials, eight cohort studies, one case-control study and one randomized controlled trial of intra-epidemic use of the vaccine. (5)

After also contacting all vaccine manufacturers and the authors of all relevant studies, the investigators only found two small studies that assessed the effects of influenza vaccines on hospital admissions (the alleged reason for the CDC's ACIP recommendation) and could not identify a single study that assessed reductions in mortality, serious complications or even community transmission of the disease.

Following a review of all the information, the authors came to two conclusions concerning the use of inactivated influenza vaccines in children younger than two years of age:

•  There was no evidence of the effectiveness of the vaccine or reduction in symptomatic cases

•  The efficacy of the vaccine, reduction in laboratory-confirmed cases was similar to that of placebo


The same Cochrane team published in The Lancet in October 2005 an equally impressive review about influenza vaccination in the elderly. It was titled “Efficacy and effectiveness of influenza vaccines in elderly people: a systematic review.” (6)

Here again, after searching five electronic databases in any language to December 2004, they reviewed 64 randomized, cohort, and case-control studies to assess vaccine efficacy against influenza (reduction in laboratory-confirmed cases) or vaccine effectiveness against influenza-like illness (reduction in symptomatic cases). Their interpretation of the findings after this comprehensive research was that “In long-term care facilities, where vaccination is most effective against complications, the aims of the vaccination campaign are fulfilled, at least in part. However, according to reliable evidence the usefulness of vaccines in the community is modest.”

The CDC obviously had to publish its own very optimistic “ Information for Health Care Professionals ” on the “Efficacy and Effectiveness of Inactivated Influenza Vaccine”. A careful “reading between the lines” reveals that the main US vaccine agency seems to concur, in veiled terms. (7)

[The CDC document is only a page-long and well-worth reading in its entirety.]

The CDC statement started: “The effectiveness of inactivated influenza vaccine depends primarily on the age and immunocompetence of the vaccine recipient and the degree of similarity between the viruses in the vaccine and those in circulation. The majority of vaccinated children and young adults develop high postvaccination hemagglutination inhibition antibody titers. These antibody titers are protective against illness caused by strains that are antigenically similar to those strains of the same type or subtype included in the vaccine.”

The statement went on:

Re Children aged > 6 months: “ …the antibody response among children at high risk for influenza-related complications might be lower than among healthy children… No effectiveness was demonstrated among children who had received only 1 dose of influenza vaccine, illustrating the importance of administering 2 doses of vaccine to previously unvaccinated children aged <9 years.

Re Adults Aged <65 Years: “ In a case-control study of adults aged 50--64 years with laboratory-confirmed influenza during the 2003--04 season when the vaccine and circulating viruses were not well matched, vaccine effectiveness was estimated to be 52% among healthy persons and 38% among those with one or more high-risk conditions.”

Lastly Re Adults Aged > 65 Years: “ Older persons and persons with certain chronic diseases might develop lower postvaccination antibody titers than healthy young adults and thus can remain susceptible to influenza infection and influenza-related upper respiratory tract illness. A randomized trial among noninstitutionalized persons aged > 60 years reported a vaccine efficacy of 58% against influenza respiratory illness, but indicated that efficacy might be lower among those aged > 70 years… Among older persons who do reside in nursing homes… the effectiveness in preventing influenza illness often ranges from 30% to 40%.” [End of quote]


Influenza Vaccination During Pregancy

In an effort to vaccinate everyone in the United States against influenza every year , the ACIP recently recommended the vaccination of all pregnant women during all trimesters of pregnancy. I had the privilege to co-author a comprehensive review of the issue with David M. Ayoub MD and our critique of this preposterous ACIP recommendation can be found at


The Canadian Experience

In May 2006, Kwong, Sambell, Johansen et al of the Institute for Clinical Evaluative Sciences in Toronto published a review titled “The effect of universal influenza immunization on vaccination rates in Ontario.” (8)

They revealed that “Between 1996/97 and 2000/01, the increase in the overall vaccination rate in Ontario was 10 percentage points greater than the increase in the other provinces combined. Increases in Ontario were particularly pronounced among people who were: younger than 65, more educated, and had a higher household income. Between 2000/01 and 2003, vaccination rates were stable in Ontario , while rates continued to rise in the other provinces. Even so, Ontario 's 2003 rates exceeded those in the other provinces.”

In June 2006, Groll and Thomson of the Faculty of Health Sciences at the University of Ottawa published a review about the effectiveness of the universal influenza immunization program in Ontario . Their article, titled “Incidence of influenza in Ontario following the Universal Influenza Immunization Campaign” was published in Vaccine .

The authors wrote: “The purpose of this study was to determine whether the incidence of influenza in Ontario , Canada has decreased following the introduction of the Universal Influenza Immunization Campaign (UIIC) in 2000… Despite increased vaccine distribution and financial resources towards promotion the incidence of influenza in Ontario has not decreased following the introduction of the UIIC.” (9)

The following table lists the number of doses of vaccine administered and the cost to the Province of Ontario during the year preceding the UIIC, the first year of the campaign and the last year reviewed.


Vaccine Doses


Vaccine Cost

(C. $ million)

Total Cost

(C. $ million)













Province of Ontario , Canada

Number of doses of Influenza vaccine administered

& Cost (Canadian Dollars)

In summary: In spite of the immense effort, a 189% increase in vaccination rates and a 467% increase in cost, the incidence of influenza in Ontario did not decrease.


U.S. and Worldwide Seasonal Effectiveness

In March 2006, the CDC published information about week 9 ( February 26 – March 4, 2006 ) and reviewed the seasonal laboratories findings. (10)

During week 9, influenza activity increased in the United States and yet only 701 specimens or 21.6% of the specimens submitted to the U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories were positive for influenza. In other words, among patients believed to have influenza and deemed worth culturing only 1 in 5 had laboratoy confirmation that indeed he or she carried the influenza virus. It should obviously be noted that the presence of a virus in the upper respiratory passages does not always mean that a clinical illness is due to that virus. Of the 701 specimens tested, 175 were influenza A (H3N2) viruses, 20 were influenza A (H1N1) viruses, 399 were influenza A viruses that were not subtyped, and 107 were influenza B viruses .

The laboratory positive results since the beginning of the season were also disturbing: “Since October 2, 2005, WHO and NREVSS laboratories have tested a total of 89,513 specimens for influenza viruses and 9,143 (10.2%) were positive. Among the 9,143 influenza viruses, 8,546 (93.5%) were influenza A viruses and 597 (6.5%) were influenza B viruses. Three thousand six hundred seventy-five (43.0%) of the 8,546 influenza A viruses have been subtyped: 3,590 (97.7%) were influenza A (H3N2) viruses and 85 (2.3%) were influenza A (H1N1) viruses.”

Because of the results, WHO scientists recommended that “ the 2006-07 trivalent influenza vaccine for the Northern Hemisphere contain A/New Caledonia/20/99-like (H1N1), A/Wisconsin/67/2005-like (H3N2), and B/Malaysia/2506/2004-like viruses. The influenza A (H3N2) and the influenza B components have been changed from the 2005-06 season vaccine components. A/Wisconsin/67/2005 is an antigenic variant of the current vaccine strain A/California/07/2004. Influenza B viruses currently circulating can be divided into two antigenically distinct lineages represented by B/Yamagata/16/88 and B/Victoria/2/87 viruses. The updating of the influenza B component to B/Ohio/1/2005 (which is antigenically equivalent to B/Malaysia/2506/2004) represents a change to the B/Victoria lineage. This recommendation was based on antigenic analyses of recently isolated influenza viruses, epidemiologic data, and post-vaccination serologic studies in humans.”

Clearly the influenza vaccine for the coming season (2006-2007) will be radically changed in an effort to combat the anticipated and ever changing community strains.

The WHO and its Collaborating Centers for Disease Surveillance will continue to diligently watch the upcoming influenza season and all related viral studies.

In an Electronic Publication ahead of print in Vaccine on June 9, 2006 , (11) Legrand, Vergu and Flahault of the University Pierre et Marie Curie wrote under the title “Real-time monitoring of the influenza vaccine field effectiveness”:

“Twice a year, the World Health Organization recommends the composition of the influenza vaccine depending on the strains which circulate several months before the beginning of the epidemic. Therefore, it is important to assess the field vaccine effectiveness (FVE) yearly. Thanks to data on vaccine coverage and data on influenza like illness cases collected by the French Sentinel Network, we are able to estimate the FVE few weeks after the beginning of the yearly influenza epidemic. In this paper, we have analysed the estimates obtained for the last 10 epidemic seasons for people over and under 65. Making the assumption that the vaccine coverage is stable from 1 year to another, we are able to assess the level of the FVE few weeks after the beginning of the epidemic and we should detect a lack of effectiveness of the vaccine.”

It is not clear what the authors exactly meant by the last sentence: “And we should detect a lack of effectiveness of the vaccine.” It certainly does not sound like a confidence-builder.


In summary, the available information from several carefully designed comprehensive reviews suggests that even if influenza vaccination was totally safe and innocuous, its effectiveness and efficacy are limited and its cost disproportionately prohibitive. 


  1. Simonsen L, Reichert TA, Viboud C, Blackwelder WC, Taylor RJ, Miller MA. Impact of influenza vaccination on seasonal mortality in the US elderly population. Arch Intern Med. 2005 Feb 14;165(3):265-72. PMID: 15710788
  2. Boyles S., Do Flu Shots Save Lives? WebMD February 14, 2005
  3. CDC, Morbidity abd Mortality Weekly Report MMWR December 17, 2004 / 53(49);1147-1153
  4. Neff MJ, Practice Guidelines: ACIP Releases 2004 Guidelines on the Prevention and Control of Influenza
  5. Jefferson T, Smith S, Demicheli V, Harnden A, Rivetti A, Di Pietrantonj C. Assessment of the efficacy and effectiveness of influenza vaccines in healthy children: systematic review. Lancet 2005 Feb 26-Mar 4;365(9461):773-80. Review.
  6. Jefferson T, Rivetti D, Rivetti A, Rudin M, Di Pietrantonj C, Demicheli V. Efficacy and effectiveness of influenza vaccines in elderly people: a systematic review. Lancet. 2005 Oct 1;366(9492):1165-74.
  7. CDC: Information for Health Care Professionals ” on the “Efficacy and Effectiveness of Inactivated Influenza Vaccine.”
  8. Kwong JC, Sambell C, Johansen H, Stukel TA, Manuel DG. The effect of universal influenza immunization on vaccination rates in Ontario .
    Health Rep. 2006 May;17(2):31-40. PMID: 16716034
  9. Groll DL, Thomson DJ. Incidence of influenza in Ontario following the Universal Influenza Immunization Campaign. Vaccine. 2006 Jun 12;24(24):5245-50 PMID: 16624458
  10. CDC Weekly Report: Influenza Summary Update, Week ending March 4, 2006-Week
  11. Legrand J , Vergu E , Flahault A . Real-time monitoring of the influenza vaccine field effectiveness” 2006 Jun 9; [Epub ahead of print] PMID: 16806607

F. Edward Yazbak , MD , FAAP

Falmouth , Massachusetts 02540

August 22, 2006

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