October 13, 2006
Bird Flu Vaccines Cross-Strain Benefit

Bottom line: If you got a vaccine shot from one strain of H5N1 bird flu and then later got a different vaccine shot for a different strain of H5N1 bird flu you'll get a stronger immune response from the second shot. That means if you got vaccine to an old H5N1 strain now and then an avian flu pandemic happened and you get a vaccine shot for the killer pandemic strain you'll get a strong immune reaction and better resistance because you had the earlier shot of a different strain. Vaccination by one strain of bird flu increases the immune response to a later strain of bird flu.

Officials were able to track down 37 people who agreed to take part. Each had received two shots as part of the vaccine study in 1998 against the form of the virus that had emerged in Hong Kong. Earlier this year each was again vaccinated with another shot targeting a different form of bird flu, the variant that swept through Vietnam in 2004 and 2005. Their immune response to the second shot was compared to the response in people who received shots for the first time in 2005. More than twice as many people who also received the shot in 1998 developed a protective antibody response against bird flu compared to people who had never been immunized against bird flu previously.

"We studied a relatively small group, so that certainly, this issue needs to be studied more thoroughly in a larger group of people," said John J. Treanor, M.D., professor of medicine and director of Rochester's Vaccine and Treatment Evaluation Unit. "If the findings hold up, then it might open up a number of options beneficial for planning. One might consider giving a priming shot to members of the community who would be a central part of the response if a pandemic were to occur, such as health care workers. You'd have people who were prepared as much as possible in advance."

The work is being presented at IDSA by research fellow Nega Ali Goji, M.D., who did the study with Treanor

The work addresses one of the features of bird flu that makes a potential pandemic so hard to fight: Like human flu viruses, bird flu mutates constantly, and by the time a vaccine has been produced to protect against one form of bird flu, it's very possible that another form, requiring a different vaccine, will have emerged that can move from person to person.

The results of the new study are similar to what doctors already know about giving "regular" flu shots. Every year millions of adults get an updated flu shot every year one shot is enough, because their immune systems "remember" previous forms of the flu and help make the new shot each year effective. But small children who have never seen the flu before typically need two shots, a primer and a booster. The results from the new study indicate that, like small children who receive a regular flu shot, adults who have never encountered bird flu would benefit from a booster shot.

The two vaccines used in the study target viruses belonging to different "clades" or viral families. Both are H5N1 bird flu viruses, but the Hong Kong strain from 1997 belongs to clade 3, while the Vietnam strain from 2004 belongs to clade 1. Goji and Treanor found that the shot targeting clade 3 helps the body maximize the immunization against a virus in a different clade, clade 1. In other words, using the vaccines that are available now might help improve the response to the vaccines developed for a future strain of bird flu.

Very likely vaccination against some existing strain of H5N1 avian flu would also increase immune response to an infection by a future pandemic strain of avian flu. This means your odds of survival from a pandemic infection would be increased if you could only get yourself vaccinated against an existing known strain of bird flu.

These results argue for mass producing a bird flu vaccine using known strains. If such a vaccine was available I'd go get a shot. Partial immunity would be much better than boxes of N95 face masks.

Share |      Randall Parker, 2006 October 13 09:35 PM  Dangers Natural Bio

Bob Badour said at October 14, 2006 6:39 AM:

My thoughts exactly! Why immunize emergency response workers when we potentially have years of advance notice to produce vaccine to immunize everybody?

Certainly, when the pandemic hits, we would immunize emergency workers with the targeted strain first before we have supplies for everybody. But for the "booster", why not start now and immunize everbody?

How much would it be worth for the US and Europe to avoid a pandemic entirely? How much would it cost to immunize all of Africa and South Asia? If partial immunity even slowed the spread, that could make a big difference.

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