For starters: “flu” shots do not prevent “stomach flu”. This idea is a miss-translation among slang languages. Influenza is a totally different disease from gastroenteritis. Furthermore influenza vaccines are purified in recent years so that they no longer cause severe fevers and aching as an after effect.
Influenza is a serious virus infection which briefly but thoroughly disables even healthy young adults. Its symptoms are fever, chills, aching muscles, sore throat and cough with significant mortality. Worldwide epidemics (pandemics), which have been occurring every few decades, have each caused millions to tens of millions of deaths.
Solid recent research demonstrates that the “wild” natural reservoir of influenza virus is chickens and ducks particularly in Southeast Asia. The “Asian flu” of a few years ago obtained its nickname from this insight. The currently prevalent avian virus circulates in fowl and occasionally infects nearby humans. Only when person to person infection emerges from a new strain does a human epidemic ensue. Pigs and other animals have also been infected en route to human transmission, hence “swine flu”.
In the last couple of years there have been in Asia a small number of human deaths from this “bird flu” (avian influenza), but human to human transmission has not occurred at least not with any regularity. Public health authorities are concerned that we are ripe for a major pandemic. A likely precipitating event would be even one person simultaneously infected with an existing strain of human influenza and one of the new strains of avian influenza. This could permit a hybrid virus to emerge capable of efficient person to person transmission.
Influenza vaccines have been only 60 to 80% effective. These percentages are misleading without explanation. They are calculated from the reported incidence of infection in vaccinated people compared to the simultaneous incidence in those not vaccinated regardless of the severity of the identified illness. Due to manufacturing requirements, the vaccines are developed from strains of virus selected six months or so before the vaccines become available; so the strains of virus circulating during the next flu season are usually not exact duplicates of the strains selected for the vaccine. This is because the circulating strains continue to mutate, a salient characteristic of influenza virus. The closely related strains in the vaccine reduce the severity of disease even when the vaccine fails to protect 100%.
A vaccine has been developed for the strain of “bird flu” currently prevalent in poultry and domestic water foul throughout the world. This vaccine is being stockpiled in moderate quantities for use in attempting to stop the spread of human cases in any region of the world where human to human transmission may occur. If this strategy should be successful, there would be time to incorporate the new strain in the vaccine manufactured for worldwide use as part of the existing annual vaccination program. Year in and year out, there is much influenza in various animal species (remember the swine flu when Gerald Ford was our President). The vast majority of these virus strains have not crossed the species barrier to humans; so incorporating these strains of virus in our annual flu shots would reduce the effectiveness of such a vaccine diluted with the many strains that have not (and probably would never) infect us. The special problem now with “bird flu” is its prevalence and virulence. The financing of the needed production of a vaccine that may never be used is a function of WHO (World Health Organization). WHO is appropriately becoming the world’s public health department with much assistance (so far) from member nations especially our Center for Disease Control in Atlanta.
If or when the impending influenza pandemic hits the world, those people with previous flu shots in many of the recent years will be quite likely to have partial immunity and be significantly less likely to die even if they do become ill. Note well, this means that annual flu shots are more important than usual in the next few years.
John A. Frantz, M.D.
Green County Health Committee
June 7, 2007