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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.
