Fighting the Flexible Flu

Oceans and armed might may protect nations from invading armies; nothing stops influenza. In 1918, the disease made a globe-girdling march that left 30 million dead. Modern outbreaks, though less horrendous, still pose a major public health threat. The 1968 epidemic affected more than 30 million in the U.S. alone, causing widespread school and job absenteeism and killing more than 200.

Because flu tends to erupt at ten-year intervals, doctors have been searching for a defense against the major epidemic expected to occur toward the end of the decade. Now they appear on the verge of success. Scientists at the National Institutes of Health's Allergy and Infectious Diseases branch last week announced a new vaccine that may make it possible to control the disease effectively for the first time.

Quick Change. The flu bug is a quick-change artist. It undergoes what scientists call antigenic alterations, or periodic transformations in biochemical makeup. As a result, vaccines developed to defend against one virus generation--usually too late to do much good--generally prove altogether powerless against the next. In addition, natural immunities acquired through exposure to one year's microbes may offer no protection against later models.

To overcome this obstacle, the NIH researchers--Drs. Brian Murphy, Elias Chalhub and Robert Chanock and Biologist Sandra Nusinoff--decided to beat the virus at its own flexible game. Vaccines now in use are made with a type of virus that has been killed and therefore has only limited ability to stimulate the body's immunological system. The new vaccine uses a combination of live viruses that brings about a stronger immune reaction. These active (though weakened) agents can also be grown in cultures more quickly, giving scientists a better chance of staying even with the most recent flu threat.

The virus used in the vaccine is a hybrid. Working in the NIH laboratories, the research team combined Hong Kong flu viruses from the 1968 epidemic with chemically altered samples of a 1965 strain. The result is a virus strong enough to produce immunity to the flu, but too weak to cause the disease itself.

The new vaccine base is extremely sensitive to heat and fails to function if exposed to the high (98.6DEG F.) temperature of the lungs, the place where flu viruses settle to bring on illness. Otherwise a live virus could not be used. But it thrives in the slightly lower temperatures of the nose and throat where, according to its developers, it triggers the production of the crucial antibodies.

Tested on volunteer prisoners at the Maryland House of Correction and a

District of Columbia reformatory, the vaccine, which is administered by nasal spray rather than injection, proved highly effective. Seventeen of 28 prisoners not given the vaccine came down with the flu after intentional exposure. All 17 others who were vaccinated remained free of the ailment. Nor did the men suffer any ill effects from the vaccine itself. Current flu vaccines often produce minor symptoms of the disease such as dizziness, headaches, low fever and slight nausea.

NIH officials warned that extensive trials and testing must still be conducted before the new vaccine can be licensed and made available to the public. But they are cautiously confident that the vaccine will be ready in time for the next predicted flu epidemic.

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