WHO Changed Definition of Influenza Pandemic
Cohen and Carter state that the WHO changed the definition of an
influenza pandemic by excluding reference to the words "with enormous
numbers of deaths and illness."
What the article fails to state is that the WHO made two changes; the
second change was to drop the requirement for a new sub-type with a simple
reassortant virus meaning that many seasonal flu viruses could be
classified as pandemic influenza.
A search of online web archives reveals that the WHO website had the
erased definition dating back to at least January 2003 through to July
"An influenza pandemic occurs when a new influenza virus appears
against which the human population has no immunity, resulting in several,
simultaneous epidemics worldwide with enormous numbers of deaths and
illness. ... When a major change in either one or both of their surface
proteins occurs spontaneously, no one will have partial or full immunity
against infection because it is a completely new virus. If this new virus
also has the capacity to spread from person-to-person, then a pandemic
Seroprevalence studies emerging show that substantial protions of
society had pre-existing protective antibody levels across age groups. A
new scientific study shows the full effect of Pandemic Influenza H1N1 in
New Zealand in 2009
The Ministry commissioned study, conducted by Environmental Science
and Research (ESR), estimates that 1.26 million or 29% of New Zealanders
were immune to the pandemic influenza virus by March this year. 
About 480,000 people had some immunity prior to last year’s pandemic
wave, mostly in the older age groups. An additional 780,000 were estimated
to have been infected during 2009. The highest rate of infection during
2009 was in school age children - where one in three children were
affected. Almost half of those infected showed no obvious symptoms.
14 percent of New Zealand school aged children had pre-existing
antibodies to the 2009 H1N1 virus.
If the WHO guidelines in effect at the time that the 2009 H1N1
influenza virus was identified in the USA in April 2009 then it would
never have been declared a pandemic as it was not a new sub-type, was not
causing enormous numbers of deaths and illness, and a significant number
of people had already been exposed to an immunogenically similar virus.
The fact that only one vaccination was required for all but young
children is another sign that this was not an immunogenically novel virus.
 Seroprevalence of the 2009 influenza A (H1N1) pandemic in New
Competing interests: No competing interests