Fifty-nine percent of Americans may be immune to H1N1

Researchers now believe that up to 59 percent of Americans - 183 million people - may be immune to the H1N1 virus, known as the swine flu.

This estimate was produced by the National Institute of Allergy and Infectious Diseases, which is part of the National Institutes of Health, and was published in the medical journal mBio, reports.

In addition to examining current immunity, the scientists examined where pH1N1, the post-pandemic H1N1, is headed in the future. pH1N1 can still be found throughout the world, but now at much lower levels, according to

This has occurred because people have either developed immunity from exposure to the virus or have been vaccinated. Since large numbers of people are now immune, the virus will be forced to alter itself or die out completely.

The authors of the study do not believe pH1N1 will come back in a dramatic fashion, as happened in 1918 with the Spanish flu, because too many people are immune, reports. The numbers of immune people can only rise, since the 2010/2011 seasonal influenza vaccine also protects against pH1N1.

There is still cause for caution, the authors say, because there is much unknown about how viruses adapt due to high levels of immunity. The best protection, they say, is to maintain immunity levels through the vaccination of anyone over the age of six months.

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