In a paper titled, "The 2009 H1N1 Pandemic Influenza Virus: What Next?" they note that 19% of Americans (60 million people) had immunity even before the swine flu outbreak was identified in Mexico in March 2009, based on seroprevalence data. They estimate another 20% of Americans (61 million people) were naturally infected since March 2009 with the swine flu virus.
The authors write,
Given the relatively low number of infections estimated so far for persons older than 50 years and the possibility that standard measurements may underestimate immunity, there may be a higher degree of population protection than predicted. [i.e., greater than 59%--Nass]
... we do not know the extent to which preexisting cross-reactive antibodies can prevent infection or disease. It is noteworthy that in past pandemics (e.g., the 1957-1958 pandemic), significant numbers of persons with probable prior exposures but without detectable cross-reactive antibodies seem nevertheless to have been protected, as were some people with low-level cross-reactive antibodies against distantly related viruses
Which begs several questions: If a majority of us are already immune to H1N1 (swine) flu, how many of us are immune to the other components of this year's flu vaccine? If those vaccinated last year are considered still immune to swine flu, aren't those people vaccinated last year with the seasonal flu vaccine still immune, in general, to the other components of this year's flu vaccine?
Since H1N1 is not a highly virulent virus, and there remain significant questions about the safety of the 2010 vaccine, especially in children, why are we pushing universal vaccination against it?
Why not do serologic testing and only offer vaccine to the minority of Americans who remain susceptible?
And how can you possibly justify firing workers who refuse vaccination when they may already be immune to what the vaccine contains? I'd love to see that litigated in a courtroom, especially for healthcare workers who are likely to have much higher levels of immunity that the average person, since they are in contact with those who are sick!