Why some people develop lifelong immunity from influenza

According to the CDC’s latest figures, more than 14,000 people have already gotten hit with the influenza virus this winter. But why is it some people seem to avoid it, year after year after year?

New research published in the journal Science may help explain why some people seem to develop a natural, lifelong immunity to certain strains of the flu. HINT: It has nothing to do with getting flu vaccines.

I’ll tell you all about this natural secret in a moment. But first let’s back up…

Influenza is a complicated infection. Experts consider it “zoonotic,” which means it arises from animal sources and then infects humans. In fact, each year poultry and swine populations in South China interact and give rise to a new strain of the influenza virus, of which there are different subtypes.

In some years, the viruses are more contagious, meaning that they transmit more easily from one person to the next. And some years they are more virulent, meaning they are more severe and deadly than other years. The especially virulent 1919 “Spanish flu” epidemic killed tens of millions of people worldwide.

As you may recall, I was the first to propose that molecular biologists analyze the virus from autopsy specimens of soldiers who died of the Spanish flu in 1919, which had been archived in the collections at Walter Reed National Military Medical Center. I managed these archived collections between 1986 and 1995. Some of these scientists have made careers out of pursuing my idea.

But there is another factor at work that explains variations in how susceptible you are to the influenza virus: the year you were born.

Birth year affects infection rates

A team of U.S. scientists recently realized that people born in different years had unexplained responses to two influenza viruses of global concern — H5N1 and H7N9. In other words, they noticed a pattern of infection emerge that is related to birth year. For example, they noticed much higher rates of infection among people born in 1960 than in 1963.

As it turns out, your age determines when you were first exposed to different influenza viruses, as the different annual epidemics occurred over time. The very first influenza viral infection that you got gives you lifelong protection against severe disease from those specific viral subtypes (HA, or hemagglutinin) within the same family of viruses.

The scientists called it “imprinting.”

The protective effect, in these different age groups of people, against the different HA viral subtypes provides 75 percent protection from having a severe case of flu, and 80 percent protection from dying from both H5N1 and H7N9 influenza virus.

This discovery allows epidemiologists to predict the specific age groups that will be more or less susceptible to severe disease from future influenza pandemics.

This factor also accounts for why some age groups appear relatively immune to different influenza viruses from one year to the next. It has nothing to do with the ineffective flu vaccinations. These people simply have a kind of lifelong immunity to the flu, depending upon which flu virus was in circulation when they had their first case of the flu.

Natural, lifelong immunity is the best kind

Children used to develop natural, lifelong immunity after exposure to other common childhood viral infections, such as chicken pox. Except now, doctors dole out vaccines by the dozens for these childhood viruses.

We still need more science — and perhaps fewer crony capitalist vaccination injections — to improve our so-called “science-based” medical practices, and actually make them more scientific.

The authors of the new study suggest that more scientific understanding will open more opportunities for rational influenza risk assessment, instead of blind, blanket “one-size-fits-all” recommendations that don’t work more than half the time, for more than half the people.


“Potent protection against H5N1 and H7N9 influenza via childhood hemagglutinin imprinting,” Science 2016 Nov 11; 354 (6313): 722-726