Is yearly influenza vaccination of children a bad idea?

6 November 2009

swordThe suggestion that yearly immunization against influenza might make children more susceptible to serious disease during a pandemic has generated some controversy. Does this idea have merit?

If you have read “Being older is a good defense against 2009 H1N1 influenza”, you are familiar with the concept of ‘heterosubtypic immunity’. After natural infection with influenza virus, the host produces T and B cells directed against internal proteins of the virions. These viral proteins are more conserved among different strains than the surface glycoproteins HA and NA. Upon infection with a different subtype – which occurs during a pandemic – heterosubtypic immunity could limit virus replication and reduce disease and death.

Evidence for heterosubtypic immunity to influenza virus comes mainly from studies in guinea pigs and mice. It has been suggested that this type of immunity could explain why older people appear to be less susceptible to infection with the 2009 H1N1 influenza virus.

What does heterosubtypic immunity have to do with vaccinating children against influenza? Immunization of children against influenza is a good idea, because it reduces the amount of disease. But immunized children don’t develop heterosubtypic immunity – it’s not induced by the vaccine, and natural infection is prevented. This could put children at greater risk for more serious disease when pandemic strains emerge. Absence of heterosubtypic immunity might explain why young children are more likely to develop severe disease after infection with the 2009 H1N1 influenza virus.

Is there a solution to this potential problem? One possibility is more widespread use of infectious, attenuated influenza vaccines such as Flumist, which are known to induce heterosubtypic immunity. New vaccines that induce heterosubtypic immunity are under development. These consist of purified internal virion proteins, such as M2 protein, that undergo less antigenic variation than HA or NA.

Should we stop immunizing young children against influenza, and wait for the development of better vaccines? Of course not! Influenza in children can be serious. We should not allow this preventable disease to occur based on an unproven theory that children might be better off in a future pandemic. Neither do the authors of the hypothesis advocate cessation of immunization:

More research is needed to find out if heterosubtypic immunity contributes to protection against infection with pandemic strains in people and if yearly vaccination against seasonal influenza prevents the induction of heterosubtypic immunity. The development and use of vaccines that can induce broad protective immunity might be a solution for these potential problems and we think this is a priority.

The results of animal experiments do not dictate immunization policy. But what we learn from animal experiments often lead to hypothesis which can be tested by studies in humans.

Bodewes R, Kreijtz JH, & Rimmelzwaan GF (2009). Yearly influenza vaccinations: a double-edged sword? The Lancet infectious diseases PMID: 19879807

Heikkinen T, & Peltola V (2009). Influenza vaccination of children. The Lancet infectious diseases PMID: 19879806

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  • michael

    Even if this were so, the pandemic year is exactly the year you do want a child vaccinated.

    Suppressing all forest fires isn't considered good policy. But there are forest fires worth putting out. You've talked about the case for season flu vaccination being reasonable but arguable. For which groups and ages is it strongest?

  • epringle

    We should still expect a CD8+ T cell response to inactivated vaccine due to MHC cross-presentation by dendritic cells at the site of inoculation.

    The evidence in Bodewes et al., was based on a subunit vaccine, not an inactivated virus. The J Immunol aritcle [He et al., 2006] they cite in support shows that live attenuated virus produce a strong CD8 response however they also show a lesser, but still greatly increased CD8 response with inactivated virus.

    What concerns me here is original antigenic sin. If we vaccinate with attenuated virus we may prevent a protective immune response to a more virulent strain in the future. We do not observe substantial original antigenic sin in inactivated virus vaccines.

  • marketa

    hi, im researching lot of websites on this theme, but it is not clear to me, as im no scientist, but mother of 2 young chilldren, due to be vaccinated.. if there is a new strain of flu, will not be their imune system weekened after the vaccination?
    can you please let me know?

  • http://www.virology.ws profvrr

    On the contrary, immunization boosts the immune response.

  • marketa

    thanx for reply, i try to make my concerns a bit clearer.. lets assume they get their vaccine, that protect them from this “swine” flu, but the flu mutates, their antigenic sin would not recognize the new strain and thats why it coud not protect them against it..the same as if you get seasonal flu shot, it wud not help u much against the swine flu..am I right? and if the flu mutates to even more similar flu as the one in 1918, which caused pheumonie mostly by young healthy adults, on wiki they said, their healthy imune system was a liability, as the cytokine storm hits them..so small childrena and elderly was not as afected..so if I boost them with adjuvant, their imunte system becomes stronger, right? Its all too much at the moment, as I read reports from ukraine.. the swine flu suppose to be mild, most of the time, the same as seasonal flu, more fever and coughing, but otherwise the same. though they vaccinate as mad.. and we dont know, there is no time for all the necessery testing..there is new vacine padenza from france, which should not be as bad, as they say, no adjuvants, tested etc..
    whats other people opinion?

  • marketa

    thanx for reply, i try to make my concerns a bit clearer.. lets assume they get their vaccine, that protect them from this “swine” flu, but the flu mutates, their antigenic sin would not recognize the new strain and thats why it coud not protect them against it..the same as if you get seasonal flu shot, it wud not help u much against the swine flu..am I right? and if the flu mutates to even more similar flu as the one in 1918, which caused pheumonie mostly by young healthy adults, on wiki they said, their healthy imune system was a liability, as the cytokine storm hits them..so small childrena and elderly was not as afected..so if I boost them with adjuvant, their imunte system becomes stronger, right? Its all too much at the moment, as I read reports from ukraine.. the swine flu suppose to be mild, most of the time, the same as seasonal flu, more fever and coughing, but otherwise the same. though they vaccinate as mad.. and we dont know, there is no time for all the necessery testing..there is new vacine padenza from france, which should not be as bad, as they say, no adjuvants, tested etc..
    whats other people opinion?