Friday, December 31, 2010

Influenza vaccination in Beijing schools


Congratulations to the Chinese government and health officials on conducting an excellent assessment of the vaccine effectiveness of 2009 H1N1 influenza vaccine. The landmark study was recently published in the New England Journal of Medicine. The vaccine was administered to over 95, 000 students, who were compared to over 244, 000 unvaccinated students.  The cumulative incidence of 2009 H1N1 virus infection was 35.9 per 100,000 among the vaccinated children and 281.4 per 100,000 among the unvaccinated children, with 87.3% vaccine effectiveness.

In addition, over the course of the surveillance, 27 cases of Guillain–Barré syndrome were identified, but none of these occurred in the vaccine recipients, demonstrating better than any of the studies conducted in the United States prior to FDA approval that this vaccine is safe and effective. Incidentally, the vaccine employed in this study (PANFLU.1) was utilized by the Chinese government only after it received approval from the State Food and Drug Administration and was produced in China in accordance with the World Health Organization's recommendations, so this was not a trial using unapproved vaccine from a non-Chinese producer.

Another important follow-up note is one that directly relates to the landscape of seasonal influenza epidemics. Schools (and daycare centers) act as important loci for influenza spread. Children are typically more susceptible to influenza virus due to their naive immune systems, and they are often especially good at transmitting virus because of lack of hygiene. Thus, circumstances that congregate children, such as schools or daycare centers, will serve as excellent sources of virus transmission.  Indeed, the Chinese study also showed that school-wide influenza incidence rates were three times less in schools that had a minimum of 40% of students vaccinated, and zero incidence where vaccination was 50% or better. This immediately eliminates an important source of community-wide infection transmission, as otherwise infected students would then return to their homes and communities and further spread the virus. We currently do not have universal influenza vaccination programs in schools in the United States, but such an approach could go far in reducing the annual spread of seasonal influenza by eliminating these crucial epicenters of infection transmission in the community at large.  

4 comments:

  1. According to the National Institute of Neurological Disorders and Stroke, the cause of Guillain-Barre Syndrome is unknown. In the 1976 Swine Flu epidemic, it appeared to be initially linked to the influenza vaccine, but that was later refuted. Currently, they syndrome is rare and effects only one in 100,000. In the study by Jiang Wu, et al., there were 27 cases of Guillain-Barre Syndrome reported from their surveillance and all of these occurred in non-vaccinated students (N=244,091). This rate of incidence appears high and also indicates a correlation between the vaccine and protective effects. Any thoughts on why such high numbers among those who did not receive vaccinations?

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  2. Guillain–Barré syndrome is a kind of autoimmune disorder in which a response to foreign antigens results in activation of the immune system against your own nerve tissues. The result is a peripheral neuropathy in which the myelin, the insulating layer of the nerve, gets destroyed causing damage to their function. GB is most often observed as an “ascending paralysis” in which weakness begins in the feet and moves towards the trunk. Death usually occurs due to respiratory failure when the nerve damage reaches those nerves innervating the diaphragm.

    It is very true that GB is a very uncommon disorder. It is also very unpredictable. Campylobacter jejuni is the most common antecedent infection, but most cases are of unknown cause. It is still unknown what are the factors that put someone at increased risk at developing GB after an infection.

    -Becca

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  3. When Guillain-Barré is preceded by a viral or bacterial infection, it is possible that the virus has changed the nature of cells in the nervous system so that the immune system treats them as foreign cells. It is also possible that the virus makes the immune system itself less discriminating about what cells it recognizes as its own, allowing some of the immune cells, such as certain kinds of lymphocytes and macrophages, to attack the myelin. It might be that G-B is only uncommon on it's own but the viral infection in this instance might have increased the incidence seen in the study.

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  4. This study shows some encouraging results on the effectiveness of the H1N1 influenza vaccine on limiting the transmission of H1N1 amongst school age children. I am curious to know what prevents a universal H1N1 influenza vaccination program from being enacted in educational settings throughout the US (other than the obvious laws and policies). How much has the debate surrounding Autism and Vaccination hindered potential Influenza vaccine programs from entering educational settings? Also, has the misconception that the Influenza vaccine will actually give people the flu or make them sick hindered these programs in any way?

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