H1N1 Vaccine Failure In Europe Recombinomics Commentary 13:29 March 2, 2010
Both, seasonal and pandemic vaccination 4 Not full pandemic vaccination 0 Not vaccinated 11 Pandemic vaccination 1 Seasonal vaccination 1 Unknown 2 TOTAL 19
The above numbers reflect the vaccination status of SARI (Severe Acute Respiratory Illness) patients in Europe, as reported by the ECDC for week 7. Five of the nineteen patients had been vaccinated against pandemic H1N1, yet still were hospitalized with severe disease. This high frequency of vaccinated patients in this population raises concerns that vaccine failure against the emerging pandemic H1N1 is widespread, because the frequency of vaccinated to non-vaccinated patients in the severe group is similar to overall population, indicating little vaccination benefit.
Similar results were reported in the United States. Although the CDC does not report vaccination status of hospitalized patients, recent media reports on three severe H1N1 patients that required airlift from Wyoming to Utah included an EMT who had also been vaccinated previously.
Vaccine failures are not unexpected due to several factors. The vaccine target worldwide is a California/7 strain that differs from the vast majority of pandemic H1N1 in circulation. There are approximately five amino acid differences, which varies slightly based on the version of California/7 being used in the vaccine, and although most samples do not show a four fold decrease in the titer when compared to the vaccine target, recent low reactors in Europe have raised concerns that a single amino acid change in multiple locations can push the isolate to the low reactor status, which would lead to vaccine failure in a large number of patients, and two changes, which have been reported, would likely increase titer reductions and create widespread failures.
In addition, pandemic waves are created by a virus that is not well recognized by most of the population initially, and a given wave ends when immunity is established. A new wave begins when this immunity is defeated by immunological escape, which would also lead to vaccine failure. However, it is generally thought that vaccinations would reduce the severity of the infections, but the recent results from Europe and the United States have raised the possibility that such reductions may be uncommon.
The lower number of cases has significantly reduced testing of patients, including severe cases. Since all three pandemics in the last century had a winter/spring wave that followed a fall wave, an increase in testing is warranted. Current surveillance only tests a small percentage of patients, including severe cases. Many hospitals use a rapid test, which in some circumstances only detects 10% of H1N1 infected patients, leading to false negatives and a gross underestimate of severe and fatal cases.
Serious testing is long overdue, and the poor surveillance and management of this pandemic remains problematic.
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