More information was released today that supports the earlier hints of AH1N1-2009 not being an entirely novel virus for all of us.
By Julie Steenhuysen
Older people who have been infected with or vaccinated against seasonal flu may have a type of immunity produced by cells that protects them from the swine flu virus, U.S. researchers said on Wednesday.
They said the pandemic H1N1 virus has parts found in earlier flu strains, and some people past age 60, who may have been exposed to similar viruses in their youth, may have some latent immune cells that protect them.
“These findings indicate that human populations may have some level of existing immunity to the pandemic H1N1 influenza and may explain why the 2009 H1N1-related symptoms have been generally mild,” said Carol Cardona of the University of California Davis School of Veterinary Medicine. Her study appears in the journal Emerging Infectious Diseases.
Cardona said cell-based immunity may be serving to weaken the effects of swine flu.
“The meaning clinically is you are going to get sick but it may not be as severe if you had no immunity whatsoever,” Cardona said in a telephone interview.
There may be quite a few people who have had an infection of the genetically related seasonal A/H1N1. I have very little doubt that I have, but I do not know for a fact, and it can be quite murky when we attempt to guess. Since 1978 there have been two strains of seasonal influenza A virus circulating, A/H1N1 and A/H3N2.
Each “flu season” one strain will represent the majority of infections, referred to as “the predominate strain”. And, now that we have A/H1N1-2009 we have actually had three strains of influenza A virus circulating, however, the predominate strain quickly became our pandemic virus – A/H1N1-2009, which now officially accounts for roughly 90% of cases typed. Only a small number of infections are typed so the exact percentage is not known, but extrapolating the ones that are tested we arrive at the 90% of the infections being from our pandemic strain.
The important take away from all of that is even if you had a case of “the flu” last year and think you might be one of the lucky ones who is walking around with a fresh load of these antibodies, you may have had a case of H3N2 and not the seasonal H1N1. Unless infections were tested and typed there is just no way of knowing beyond a guess.
If one wishes to arrive at a slightly informed guess: look up the predominate strain circulating during the time you remember being ill with a case of “the flu”. Chances are, the predominate strain is what you had. Of course, that brings up the question of whether or not you actually had a case of “the flu” in reality, or one of the other hundred odd pathogens that people often confuse with influenza.
We can guess – or we can err on the side of caution and get our pandemic vaccine. I’m going to play it safe even though I’m fairly certain I had seasonal H1N1 back in the late 70′s. For me, it’s just not worth being sick, possibly quite sick, when something so simple as a vaccine will protect me.
The Emerging Infectious Diseases paper can be found here: Ahead of Print PDF.
At “my day job” we have been offered the opportunity to receive our vaccines, seasonal and pandemic [if one can take the FluMist pandemic vaccine], I am pleased to be able to report the uptake rate has been impressive. I assume part of the success has been because our corporate HR department sent around a wonderfully informative memo explaining issues and concerns. Of course, I would like to think that a small part of the uptake numbers has been because I have answered a few questions here and there. However, it may only be coincidental that we’ve had our first cases strike within family and an employee. Whatever the threat is, it “feels” close by — that can be quite motivating, far more so than some “hypothetical – in the future – potential of becoming sick.”
Regardless of the reason[s], I am pleased and proud of the demonstration of my coworkers taking personal responsibility for their health. I could make a strong argument that those of us who are stepping up and getting our vaccines are also doing something concrete to help protect the “health” of our “community” – our fellow coworkers – the ones who do not have the foresight to protect themselves and the ones who cannot take the FluMist vaccine and are waiting for their turn at the injectable version. That wait will be several months long for some, months during which the virus will be actively circulating.