According to an article at Science Daily children who receive the flu shot might have up to three times the risk of hospitalization for the flu. The article talks about a cohort study of influenza performed at the Mayo Clinic that looked at 263 children who were seen at the clinic with laboratory-confirmed influenza between 1996 and 2006. The study verified who had received the flu vaccine and who had not and determined that children who received the flu vaccine had three times the risk of hospitalization when compared to those who had not.
I have not been able to find the original source of the study but it was supposed to be presented at the 105th International Conference of the American Thoracic Society.
After reading this article I started to wonder at how well the flu shot works in general, so I went looking for some information. What I found made me wonder at why it is pushed so much.
First a little background - there are currently two styles of flu vaccines on the market now. The first is a the flu "shot" made from inactivated (killed) virus that you get via an injection at a doctors office or some other clinic. The second is a nasal spray that contains an attenuated (live weakened) viruses. This second form is a more recent development that is not as widespread yet.
I am going to be talking about the first form only - the traditional flu shot.
So lets start with the first problem - the flu shot is one of the few types of vaccinations that still contains thimerosal (ie mercury). If you don't know why that could be a problem just google autism and mercury and prepare to wade into a holy war.
The short version is that this preservative isn't a good idea and while there are no "proven" health problems associated with it there is no reason for it to still be there. The good news is that thimerosal free versions are available but you have to ask for them.
The second problem is that the flu shot isn't that good at preventing the flu. According to the (most likely over-optimistic) CDC the flu vaccine can prevent 66% of cases of influenza in young children. But the effectiveness of the shot can vary from year to year based on how well the the shot is matched to the strains of flu that are active that year.
I also looked for published research detailing how well the flu vaccine worked in children and found a mixed bag. Some research agrees with the 66% that the CDC says while some does not. I was particularly struck by this meta study published in Lancet in 2005 that found that the effectiveness of the vaccine in children older than 2 was about 38% but in children under two performed no better than a placebo.
So at worst the shot may have no little or no real effect and may lead to a greater risk of hospitalization but at best could have a better than 66% chance of preventing the flu.
As I have written about before I am a little leery about this shot because the one time that my twins received this shot they seemed to develop the flu shortly afterwards closing followed by their regression into autism.
So, is the flu shot a good idea for kids? I think the answer is a definite maybe.
Hi MJ
ReplyDeleteThank you very much for your answer in your last blog entry.
I am going to include some abstracts of very recent manuscripts that I think are important. My autistic son never was vaccinated with the flu vaccine. He had a very mild case of swine flu last year.
Lancet Infect Dis. 2009 Dec;9(12):784-8. Epub 2009 Oct 30.
Yearly influenza vaccinations: a double-edged sword?
Bodewes R, Kreijtz JH, Rimmelzwaan GF.
Department of Virology, Erasmus Medical Center, Rotterdam, The Netherlands.
Yearly vaccination against seasonal influenza viruses is recommended for certain individuals at high risk of complications associated with influenza. It has been recommended in some countries, including the USA, that all children aged 6-59 months are vaccinated against seasonal influenza. However, it has been shown-mainly in animals-that infection with influenza A viruses can induce protective immunity to influenza A viruses of other unrelated subtypes. This so-called heterosubtypic immunity does not provide full protection, but can limit virus replication and reduce morbidity and mortality of the host. This type of immunity might be relevant to human beings when a new subtype of influenza A virus is introduced into the population, such as the new influenza A H1N1 virus responsible for the present influenza pandemic and the highly pathogenic avian influenza H5N1 viruses that are causing an ever increasing number of human infections with high mortality rates. Preventing infection with seasonal influenza viruses by vaccination might prevent the induction of heterosubtypic immunity to pandemic strains, which might be a disadvantage to immunologically naive people-eg, infants.
PLoS One. 2009;4(5):e5538. Vaccination against human influenza A/H3N2 virus prevents the induction of heterosubtypic immunity against lethal infection with avian influenza A/H5N1 virus.
Bodewes R, Kreijtz JH, Baas C, Geelhoed-Mieras MM, de Mutsert G, van Amerongen G, van den Brand JM, Fouchier RA, Osterhaus AD, Rimmelzwaan GF.
Department of Virology, Erasmus Medical Center, Rotterdam, The Netherlands.
Annual vaccination against seasonal influenza viruses is recommended for certain individuals that have a high risk for complications resulting from infection with these viruses. Recently it was recommended in a number of countries including the USA to vaccinate all healthy children between 6 and 59 months of age as well. However, vaccination of immunologically naïve subjects against seasonal influenza may prevent the induction of heterosubtypic immunity against potentially pandemic strains of an alternative subtype, otherwise induced by infection with the seasonal strains. Here we show in a mouse model that the induction of protective heterosubtypic immunity by infection with a human A/H3N2 influenza virus is prevented by effective vaccination against the A/H3N2 strain. Consequently, vaccinated mice were no longer protected against a lethal infection with an avian A/H5N1 influenza virus. As a result H3N2-vaccinated mice continued to loose body weight after A/H5N1 infection, had 100-fold higher lung virus titers on day 7 post infection and more severe histopathological changes than mice that were not protected by vaccination against A/H3N2 influenza. The lack of protection correlated with reduced virus-specific CD8+ T cell responses after A/H5N1 virus challenge infection. These findings may have implications for the general recommendation to vaccinate all healthy children against seasonal influenza in the light of the current pandemic threat caused by highly pathogenic avian A/H5N1 influenza viruses
From what I understand, there are
ReplyDeleteLive-attenuated influenza vaccine (LAIV) versus TIV ( Three inactivated viruses vaccines) both intramuscular plus the nasal spray vaccines.
Live attenuated influenza vaccines were analyzed by Dr Hillerman, because of the possibility of reassortant virus combination, making new lethal strains.
This is the abstract. If you can get the manuscript, for me it was really excellent. Dr Hillerman is very known in vaccine´s field.
Vaccine. 2002 Aug 19;20(25-26):3068-87.
Realities and enigmas of human viral influenza: pathogenesis, epidemiology and control.
Hilleman MR.
Merck Institute for Vaccinology, 770 Sumneytown Pike, West Point, PA 19486, USA.
Influenza A is a viral disease of global dimension, presenting with high morbidity and mortality in annual epidemics, and in pandemics which are of infrequent occurrence but which have very high attack rates. Influenza probes reveal a continuing battle for survival between host and parasite in which the host population updates the specificity of its pool of humoral immunity by contact with and response to infection with the most recent viruses which possess altered antigenic specificity in their hemagglutinin (HA) ligand. HA ligand binds the virus to the cell to bring about infection. Viral survival relies on escape from host immunity through antigenic alterations in nature which arise through genetic drift by point mutation principally of the HA gene, or through genetic shift by reassortment exchange of the HA ligand with that of viruses retained in avian species. Partial control of influenza is by use of killed whole, subunit, or possible live virus vaccines, all of which rely on worldwide surveillance to provide early detection of the altered immunologic specificity of the next virus to come. Future global surveillance may be aided by studies of sampled viral isolates in laboratories having capabilities for accelerated genetic sequencing and for automated rapid throughput analyses as well. Influenza vaccines of the future must be directed toward use of conserved group-specific viral antigens, such as are present in transitional proteins which are exposed during the fusion of virus to the host cell. Chemotherapy, though still primordial, must eventually provide the ultimate solution to vaccine failures. Probing the enigma of the severe influenza pandemic of 1918-1919 is an exciting contemporary venture in which genetic reconstruction of the viral genome from surviving archival RNA is being conducted with great success. Present evidence reveals successive recycling in pandemics, of only 3 of the 15 possible avian viral HAs. Pandemics are believed, conventionally, to be derived solely by rare events in which wild viruses of man acquire a new HA ligand of avian origin. There might be an alternative possibility involving a periodicity in selective control by the host population itself, in its receptivity or rejection at a particular time of particular reassortant viruses which might be created more frequently in nature than we are presently aware. This hypothesis, though remote, provides a different way to view and to probe the enigma of pandemic influenza.
Youngner JS, Treanor JJ, Betts RF, Whitaker-Dowling P. Effect of
simultaneous administration of cold-adapted and wild-type influenza
infections in humans. J Clin Microbiol 1994;32:750–4.
Beyer WEP, Palache AM, de Jong JC, Osterhaus ADME.
Cold-adapted live influenza vaccine versus inactivated vaccine:
systemic vaccine reactions, local and systemic antibody response,
and vaccine efficacy. A meta analysis. Vaccine 2002;20:1340–53.
The Dr Hillerman manuscript reports that Youngner et al. showed that reassortment does occur (2.4%) in humans given live cold-adapted and wild viruses simultaneously into the nose.
Of course the series of manuscripts of Jefferson et al in BMJ and Lancet are also very interesting.
WWhat do you think about?
Sorry, I made a mistake
ReplyDeleteThe injectable flu vaccines are only Inactivated.
Flu vaccines are available either as
TIV (flu shot (injection) of trivalent (three strains; usually A/H1N1, A/H3N2, and B) inactivated (killed) vaccine) or
LAIV (nasal spray (mist) of live attenuated influenza vaccine.)
I confused because of the amount of TIV in market-several
I will have to take a look at these.
ReplyDeleteDid you know that WHO changed the definition of pandemic and now they are lying about it?
ReplyDeletehttp://insidevaccines.com/wordpress/2010/01/24/pandemic-when-did-the-definition-change/
Minority,
ReplyDeleteI did see that the post on inside vaccines but I am not quite sure what to make of it.
On the one hand, if they did change the definition, they should be forthcoming about it.
But on the other hand the basic meaning didn't change in that the word is still being used to refer to a disease that spreads quickly around the world.
Well, I really don't know. In my days before, they don't have a flu shot for kids. but I think it is more better to have a flu shot for kids.
ReplyDelete-mel-