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Influenza Vaccination Of Infants: A Useless Risk

By: Dr. F. Edward Yazbak

In the spring of 2004, the Advisory Committee on Immunization Practices (ACIP) of the Centers for Disease Control and Prevention (CDC) recommended that all children 6- to 23-months of age be vaccinated against influenza because they were at "substantially increased risk for influenza-related hospitalizations." (1)

A review in The Lancet suggests that influenza vaccination of infants is useless.

The influenza vaccines

There are two types of influenza vaccines on the U.S. market.

One is the recently released intranasal live virus vaccine that is not recommended for infants and children under five. MedImmune's FluMist® will not, therefore, be discussed in this article.

The second is the older and well-known inactivated (killed) influenza vaccine that is administered by injection in the following dosage:

Children 6- to 36-months: 0.25 ml/dose
Children older than 3 years: 0.5 ml/dose
Adults: 0.5 ml/dose

Infants and young children receiving the vaccine for the first time should receive two doses one month apart. They, in fact, receive an adult dose within one 30-day period.

Only split-virus, subvirion, or purified surface antigen vaccines should be administered to children because of their decreased potential for causing febrile reactions. (1)

This year, Sanofi Pasteur will produce between 50 and 60 million doses of influenza vaccine for the U.S. market. GlaxoSmithKline (GSK) is planning to produce and sell about 8 million doses in the U.S., since the FDA licensed its product on Aug. 31, 2005. (2)

Chiron's Liverpool facility has been trying to correct its manufacturing problems
for more than a year and will need approval by the British MHRA (Medicines and Healthcare products Regulatory Agency) and the U.S. Food and Drug Administration (FDA) before it can ship out its first dose of vaccine. It is clear that Chiron is already too late for the start of the season. In the best scenario, it will provide 18 million to 26 million doses of vaccine for use in the United States.

It is evident that there will be a shortage of injectable influenza vaccine this season and that the CDC will have to promote the use of the intranasal live vaccine for those individuals for whom it is indicated. 

Presentation and Preservatives

Sanofi Pasteur (Aventis Pasteur) offers four different options in its influenza vaccine Fluzone®: three thimerosal-free single-dose presentations including a 0.25 ml syringe for children 6 months to 35 months of age; either a 0.5 ml syringe or a 0.5 ml vial for persons aged 3 years and older; and a multi-dose vial with thimerosal as a preservative, licensed for those ages 6 months and above. (
The GSK U.S. product will be available in 0.5 ml syringes containing a trace amount of thimerosal remaining from the production process. The vaccine is licensed for adult use.
Chiron, if approved by the FDA and MHRA, will provide most of their U.S. product in multi-dose vials with thimerosal as a preservative - presumably for adults. They may also provide for children over the age of 4 years and for adults some 0.5 ml syringes containing trace amounts of thimerosal. (2)
The following table summarizes the relevant FDA information on the thimerosal content of all licensed influenza vaccines as of Sept. 6, 2005. (3)

Trade Name


Thimerosal Concentration



Aventis Pasteur Inc.


25 µg/0.5 ml dose




25 µg/0.5 ml dose

Fluzone (no thimerosal)

Aventis Pasteur Inc.



Fluvirin (preservative free)


< 0.0004%

< 1 µg/0.5 ml dose



< 0.0005%

< 1.25 µg/0.5 ml dose

To date, there is no national recommendation to use thimerosal-free or preservative-free flu vaccines exclusively in infants and younger children.

The CDC recommendation seems to be that thimerosal-free brands are preferred if they are available. If not, any available inactivated flu vaccine can be used in order to "protect" the infants.

Few states have mercury-free pediatric vaccine laws. 

Influenza vaccination of infants

Is influenza vaccination of 6- to 24-month-old infants effective? 
Will it decrease influenza-related hospitalizations as claimed by the ACIP?

The answer to both questions appears to be no.

This answer is based on an extensive review published in the Feb. 25, 2005 issue of The Lancet. The authors, Jefferson, Smith, Demicheli et al, literally analyzed every available reference on the subject that they could find in the Cochrane Library, MEDLINE, EMBASE Biological Abstracts and Science Citation Index to June 2004 - in any language. They included 14 randomized controlled trials, eight cohort studies, one case-control study and one randomized controlled trial of intraepidemic use of the vaccine. (4)

The authors also:

  • Contacted the vaccine manufacturers and the authors of all relevant studies
  • And included every study ever published that compared the efficacy of influenza vaccines.

Surprisingly, they 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 they could not find a single study that assessed reductions in mortality, serious complications or even community transmission of the disease.

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

  • There is no evidence of the effectiveness of the vaccine or reduction in symptomatic cases
  • The efficacy of the vaccine, reduction in laboratory-confirmed cases, is similar to that of placebo.

In its publication Efficacy and Effectiveness of Inactivated Influenza Vaccine, dated Aug. 8, 2005 and intended to support its recommendation, the CDC concedes in its opening statement that 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. (5)

The following is all the information concerning the effectiveness of the inactivated influenza vaccine in children 6- to 23-months old that is available in that publication on the CDC web site:

"Children aged > 6 months can develop protective levels of anti-influenza antibody against specific influenza virus strains after influenza vaccination, although the antibody response among children at high risk for influenza-related complications might be lower than among healthy children"¦.

"A 2-year randomized study of children aged 6--24 months determined that > 89% of children seroconverted to all three vaccine strains during both years. During year 1, among 411 children, vaccine efficacy was 66% (95% confidence interval [CI] = 34%--82%) against culture-confirmed influenza (attack rates: 5.5% and 15.9% among vaccine and placebo groups, respectively). During year 2, among 375 children, vaccine efficacy was --7% (95% CI = --247%--67%; attack rates: 3.6% and 3.3% among vaccine and placebo groups, respectively; the second year exhibited lower attack rates overall and was considered a mild season). However, no overall reduction in otitis media was reported"¦.

"A retrospective study among approximately 5,000 children aged 6--23 months conducted during a year with a suboptimal vaccine match indicated vaccine effectiveness of 49% against medically attended, clinically diagnosed pneumonia or influenza (International Classification of Diseases, Ninth Revision [ICD-9] codes 480--487) among children who had received 2 doses of influenza vaccine. 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)."

That's it: 230 words.

A careful review of the CDC information reveals the following:

  • Antibody response among children at high risk for influenza-related complications appears to be lower than among healthy children. In other words, children who were more likely to be hospitalized had less antibody response and less benefit from the vaccination.
  • First study: During year two, vaccine efficacy among 375 children, was --7% against culture-confirmed influenza (95% CI = --247%--67%; attack rates: 3.6% and 3.3% among vaccine and placebo groups, respectively) and there was no reduction in ear infections. During year 1, vaccine efficacy was better. The study did not examine complications or hospital admissions.
  • Second study: One dose of influenza vaccine was totally ineffective. Children who received two injections of vaccine had a 49 percent reduction in "clinically diagnosed" pneumonia or "influenza." Because these were not culture-confirmed cases, the clinical illnesses may not have been due to the influenza virus or may have been due to a different strain of virus than that in the vaccine.  In either case, vaccination would not have influenced the course of the illness - one way or the other.

Jefferson and associates concluded that immunization of very young children "is not lent support by the findings" of their extensive and detailed research of the world literature and could not find convincing evidence that vaccines can reduce mortality, admissions, serious complications, and community transmission of influenza. (4)

The Lancet study was funded by Regione Piemonte, Italy, the Oxford Childhood Infection Study, University of Oxford and a program grant from the U.K. Medical Research Council (MRC). Given that the MRC and The Lancet are two historically pro-vaccine institutions, the results of this careful review must be taken very seriously.

The two studies quoted by the CDC are limited, weak and irrelevant.

The CDC and its Advisory Committee on Immunization Practices have a simple choice:

  • They can continue recommending the useless influenza vaccination of infants aged 6 to 24 months 


  • They can do the right thing and rescind the 2004 recommendation.


Now that is a tough choice!



  4. 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.


October 3, 2005

Chiron has received initial approval from the FDA to distribute influenza vaccine in the United States for the 2005-2006 season and is expected to produce 18-26 million doses. According to a company spokesperson, each 0.5 ml dose of the Chiron vaccine will contain 25µg of mercury.

Sanofi Pasteur will also produce 50 million doses for the U.S. market and GlaxoSmithKline 8 million doses.

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