People need to be vaccinated against flu every year. This is because the flu virus is a scam artist: it uses a big, showy surface protein to attract your immune system, then changes it so your immune system would not recognize it next time round. Vaccines must change yearly to match it.

Worse, there are sixteen different varieties of this protein, called Hemagglutinin (HA), and immunity to one does not work on the others. Pandemics happen when flu swaps one for another, as swine flu did last year.

If we could identify a flu protein that the virus can not alter so readily, then we should be able to elicit immunity that recognizes all kinds of flu .

Mushroom stalk

New Scientist reports that last year, two groups reported a promising candidate: part of the stalk of the mushroom-shaped HA, a vital bit of viral machinery which does not vary much over time or between viruses.

One of those groups, at Scripps Research Institute in la Jolla, California, teamed up with Peter Palese and colleagues at Mount Sinai Medical School in New York to test that protein as a vaccine. They report that 54 amino acids from this bit of the stalk, linked to a protein that attracts immune reactions, induced antibodies that work against viruses from every flu family that attacks people.

These included three pandemic viruses (H1, H2, and H3), three others that attack occasionally (H6, H9, and H7), and the H5N1 bird flu from 2004 — albeit modified to make it less deadly.

Mice were injected with this protein twice, three weeks apart, to allow their immunity to develop. Two weeks after the second injection each mouse was exposed to one type of live flu virus, as were unvaccinated mice.

NS reports that the team found that doses of the viruses that killed unvaccinated mice did not kill any vaccinated mice — except for the H5N1 virus, and then more than half the vaccinated mice survived.

Vaccinated mice still became ill, but not as ill as unvaccinated mice, judging from the weight they lost, a standard measure of illness in mice.

Partial protection

The vaccine thus did not protect the mice completely, but it would be cheap and quick to make, and could stop people dying, the team say – which might be enough in a serious pandemic.

Since it does not prevent illness altogether, however, people would still need constant re-vaccination to avoid ordinary, seasonal flu. Two vaccine developers, the Israeli firm Biondvax and the American firm Dynavax, are now testing vaccines they hope will prevent ordinary seasonal flu.

A vaccine that stops several kinds of seasonal flu is badly needed. The flu season getting under way this week in the United States and Europe reveals a complex viral situation.

After previous flu pandemics, the viruses that were circulating beforehand have disappeared, replaced by the pandemic virus. This has not happened this time.

Swine flu seems to have replaced one formerly common flu virus, from its own H1 family, and it dominated the Australian flu season. The most deadly pre-pandemic virus, H3N1, remains common in China, south-east Asia, and Africa, and has accounted for half the U.S. cases tested this season.

NS notes that this does not bode well for the elderly, who tend to resist swine flu but are vulnerable to H3. Meanwhile, H5N1 bird flu has struck thirty-nine people last year, killing twenty, most recently two Indonesians in September.

—read more in Taia T. Wanga et al., “Vaccination with a synthetic peptide from the influenza virus hemagglutinin provides protection against distinct viral subtypes,” Proceedings of the National Academy of Sciences (18 October 2010) (doi: 10.1073/pnas.1013387107)