A FLU vaccine that is sprayed into the nose seems to protect against strains other than those it was designed for. Its developers are trying to find out why. “We don’t understand at all why this happens,” says Harry Greenberg of Stanford University, California. “But if we did we might be able to apply the same trick to other vaccines.”
Such vaccines could have huge health implications. Many viruses are able to evolve and change the surface proteins they present to the immune system, so that vaccine manufacturers have trouble keeping up. Conventional flu vaccine, for instance, contains killed vaccine from three separate strains. So each season health officials try to predict which viruses will emerge by tracking the global migration of viral strains. Sometimes they guess wrong, and the vaccine is useless.
Greenberg helped to develop FluMist, a nasal spray of a live, weakened strain of flu, as an alternative to a shot of killed virus, and has a financial interest in the vaccine’s success. Emerging data suggests that this new method of vaccination may trigger the kind of immunity that protects against a broad range of viruses. One study published in 2000 followed people who had received the vaccine for two years. In the second year, the vaccine proved 86 per cent effective against a new strain it wasn’t designed for.
Advertisement
Last season in the US, a strain of flu broke out that was significantly different from any included in vaccine preparations. Preliminary results suggest that the nose spray provided stronger than expected immunity.
Greenberg and his team told the AAAS they have now inoculated 70 people with the nasal vaccine and an equal number have had a conventional flu shot. The team will test how effectively antibodies in their blood neutralise emerging strains over the next four years.
The researchers will explore two possibilities for how the vaccine is stimulating broad protection. Either FluMist triggers production of a wide variety of antibodies, each with an affinity for different flu strains, or it triggers the formation of more flexible antibodies, which can change shape to grab the viral proteins of different strains. They also plan to investigate whether the effect is related to the mode of delivery of the vaccine or the fact that it is made from live virus.