H1N1 flu (swine flu): Can you catch it twice?
H1N1 flu (swine flu) can't reinfect you, but it's not the only flu in town.
Q: My children are just getting over the swine flu (H1N1), and I may have picked it up. If I get sick, is there a chance the kids will catch swine flu a second time, from me?
No name / No state given
After being infected with the 2009 swine flu virus, your children can't catch the same virus again — not from you, not from anyone else. All flu viruses are that way. Once you're exposed to a flu virus, your immune system develops antibodies and memory cells unique to that virus. Your body can then defend itself if you're exposed to the virus again. This system of defense is known as acquired immunity. You also acquire immunity to flu viruses when you get a flu shot or take the nasal flu vaccine.
If having the flu or getting vaccinated gives you immunity, why is the 2009 swine flu (H1N1) virus such a problem? And why get a seasonal flu shot every year?
The short answer: Flu viruses rearrange their DNA all the time; it's how they survive. So, while your children are now immune to influenza caused by the 2009 swine flu virus, other flu viruses can still make them sick, as can many noninfluenza viruses, including those that cause colds and pneumonia.
What you're coming down with is most likely an infection with the same virus your kids had, and most flu-like illness these days is caused by the H1N1 virus. But on the off chance that you have a viral infection your children aren't immune to, it's still wise for everyone in your home to wash their hands often and cover their coughs and sneezes. You don't have to isolate yourself from the rest of the family, but give them some distance until you're well again.
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There have been proven cases of reinfection of influenza (novel H1N1). One such case was reported here: http://www.dailymail.com/News/200911041062.
The CDC reports: http://www.cdc.gov/Flu/professionals/vaccination/effectivenessqa.htm
Overall, in years when the vaccine and circulating viruses are well-matched, influenza vaccines can be expected to reduce laboratory-confirmed influenza by approximately 70% to 90% in healthy adults <65 years of age. ...The immune competence of the person being vaccinated can also affect vaccine effectiveness. For example, the vaccine may be only 30%-40% effective against influenza-related respiratory illness among nursing home residents. However, even in this group of frail elderly, the vaccine still provides substantial protection against more severe outcomes, such as influenza-related hospitalization (effectiveness of 50-60%) and deaths (80%). The presence of chronic medical conditions may also affect vaccine effectiveness. In a study of persons 50-64 years of age, the vaccine was 60% effective among otherwise healthy adults 50-64 years of age, but only 48% effective among those with high-risk medical conditions (Herrera, et al Vaccine 2006)....Among elderly persons not living in nursing homes or similar long-term care facilities, influenza vaccine has been reported to be 30%-70% effective in preventing hospitalization for pneumonia and influenza. Among older persons who reside in nursing homes, influenza vaccine is most effective in preventing severe illness, secondary complications, and deaths. Among this population, the vaccine has been reported to be 50%-60% effective in preventing influenza-related hospitalization or pneumonia, and 80% effective in preventing influenza-related death, although the effectiveness in preventing illness from influenza often ranges from 30% to 40%. In years when the vaccine is not well- matched to circulating influenza strains, vaccine effectiveness (VE) is often lower....more at above link.
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Ask the Kids' Health Expert: Dr. Jay L. Hoecker
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