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Paradigm Shift Intervention Monitoring
Since the start of the season in week
40, with 65 cases of A (H1N1) reported in 2009. A large proportion of
patients (46 pc) were not vaccinated against the influenza pandemic, 16
were missing data on vaccination status and only three patients
reported that they were vaccinated.
The above week 51 data from Sweden includes at least three cases of vaccine breakthrough for pandemic H1N1. Since the above data is incomplete, the number of categorized cases does not equal the total number of confirmed case, and a large portion of the categorized cases have an unknown vaccination status, the frequency of breakthrough is unclear, which is also true for the UK, where at least one case has been reported.
However, the rapid spread of H1N1 in the UK suggests that many who are infected this season were also infected last season, demonstrating the ability of the current virus to evade the host immune system primed by last year’s virus. Some of the sequences from the UK are derived from sequences circulating in Australia, where there were also reports of vaccine breakthrough and severe cases.
This type of immunological escape is not unusual. It is part of the natural evolution of a virus that re-emerges in the following season. The immunological escape is required for a robust return as seen in the UK, which raises concerns that the use of a vaccine target from early 2009 will have limited utility against a rapidly emerging H1N1 in 2011.
This natural evolution was largely discounted in the WHO proclamation in August declaring the end of the pandemic phase, and was also discounted by “experts” who maintained that immunity generate last season would lead to a milder season in 2010/2011. The recent reports from the UK describe a more virulent H1N1 which is causing severe and fatal illness in a higher frequency of cases, which has severely strained health care delivery of ICU beds and ECMO machines.
The return of vacationing students and workers to schools and jobs raises concerns that the spike in severe and fatal cases seen during the holiday period will intensify in the upcoming weeks raising serious health care delivery issues.
The release of UK sequences from December severe and fatal cases would be useful.