Vaccination may make flu worse if exposed to a second strain

[Celebration]

Link

A new study in the U.S. has shown that pigs vaccinated against one strain of influenza were worse off if subsequently infected by a related strain of the virus.

Microbiologist Dr. Hana Golding of the Center for Biologics Evaluation and Research at Bethesda in Maryland and colleagues at the National Animal Disease Center in Ames, Iowa and elsewhere, vaccinated "naive" piglets (those that had never been exposed to flu viruses) against the H1N2 influenza strain and later exposed them to the rare H1N1 virus, which is the virus responsible for the 2009 swine flu pandemic.
When the piglets were vaccinated they produced a wide range of antibodies to block the H1N2 virus, but these "cross-reactive" antibodies not only failed to provide protection against the second virus, H1N1, but appeared to actually help the H1N1 virus infiltrate lung tissue and cause more severe symptoms and respiratory system complications such as pneumonia and lung damage. The unvaccinated controls suffered milder pneumonia and fewer other complications. This effect is called Vaccine-Associated Enhanced Respiratory Disease.

The researchers found that the antibodies produced in response to H1N2 could not bind to a key region of the H1N1 virus and could therefore neither kill nor neutralize them and stop them binding to cells in the pigs' lungs, and in fact helped the new virus to fuse to lung cells and multiply more readily, through a process the scientists dubbed "fusion enhancing."

The team concluded that this effect should be taken into consideration by researchers trying to develop a universal influenza vaccine to protect humans from all strains of flu virus, since protection against one strain may produce antibodies that assist similar, related strains of virus. They also cautioned that their results may not apply to humans, and that the vaccines they used were made from whole, killed viruses, unlike those used to protect humans, which are made from parts of killed viruses.

The current findings add weight to studies of the 2009 outbreak of H1N1 flu in Canada, which discovered that people who had received the normal seasonal flu vaccine were more likely to be affected by H1N1 than those who had not been vaccinated.

[longship]

1. I want to see this go through peer review.

It doesn't pass the smell test on first reading. It seems to be counter to how vaccines work.

I am no expert, but I'd like to see what other experts say about this before I would pass judgement on it.

[Robb]

2. It makes some intuitive sense.

When you stimulate the body to produce antibody X, you're taxing the system to do so. When virus Y comes along, you're statistically more susceptible because your system is tuckered out already?

[longship]

3. Well, not if the two viruses are related.

Now I am really over my head. But H1N1 and H1N2 are related in that they have a common activation -- is that what you call it? -- the H1 part.

That would mean antibodies for H1N1 should provide at least partial immunity to the related H1N2 strain.

I remember reading about this from Mark Crislip a few weeks back and his job is fighting infectious diseases in a clinical environment. He was talking about two other strains of flu, but this case seems parallel. He reported that immunization to the seasonal flu conferred partial immunity to the bird flu, a different strain.

So I am very skeptical of this finding. That's why I reserve my opinion until the peer review comes in. As so should everyone. A single study is never definitive in science. When a single study breaks with existing science (even if that's only a minor break) one should be doubly skeptical.

[hedgehog]

4. All vaccinations are a matter of playing the odds -

if the findings are accurate, this year's vaccine against Flu type ABC will protect you against the type of virus you are most likely to encounter - ABC. It's possible but unlikely that you would encounter virus XYZ. So, even if your case of XYZ would be worse because you're immunized against ABC, overall the odds are better that you be vaccinated.

It's similar to wearing seat belts - there is a chance you would be trapped in a burning car, but the chances of going through a windshield are almost a certainty, so you're better off wearing a seat belt.

[SheilaT]

5. How interesting.

Although this does seem to confirm that getting immunity from actually getting the flu is far and away the best.

Yes, I get it that there are those of you out there who won't do well at all if you get real flu. And you should absolutely be getting the flu shots. Perhaps these studies will help refine what exactly should be put in the vaccinations.

Here's something else I don't fully get about the flu shots. How long is the specific immunization supposed to last? A season? Two, three? Forever?

I do know that in 1918, when the "Spanish Flu" swept the world and killed so very many people, the main reason those over 60 almost never got it or died, was because about 50 years earlier a flu epidemic of another type A flu (the kind the Spanish flu was. Type A flu is invariably the worst, most virulent and deadly) and so those old enough to have been exposed to the earlier version were already immune.

I have already lived through the earlier type A flu pandemics: the Asian flu of 1957 and the Hong Kong flu in 1968. I think I got flu in 1957. I was only 9 that year, so I'm not 100% certain. I do know I did not get flu in 1968 or '69. But I recall being pretty sick sometime earlier, which means I'm basically immune to any type A flu.

Those of you born a lot later, those of you who aren't keen on being sick for a week or so, absolutely take the shots. But I still come back to the basic question of how long does the immunity from the shot last? Or is it only for the specific sub-type of flu in the shot?

[uppityperson]

6. Each vaccine is for only a few varieties as influenza virus mutates all the time

the vaccine you get is only for those types in it.

Think of the virus as a a lego creation. The kid making the lego creation periodically adds a piece, takes off a piece, substitutes one piece for another.

A vaccine inspires your immune system to make antibodies for that specific virus/lego creation. The antibody fits the virus/lego creation exactly.

A vaccine is for only a couple specific viruses/lego creations. If the virus/lego creation is slightly different, the antibodies produced after the vaccine won't fit it, won't do anything.

This is also why the vaccine for measles, another virus, does nothing for influenza. They are different shapes, so the antibodies do nothing.

Once your body has made the antibodies, if that specific virus enters your system later, your body should be able to deal with it more quickly since the blueprints for the antibodies are already present in your body.

Of course it is more complicated that that, organs, cells, etc, but this is a good analogy, hope it makes sense.