Does the Flu Vaccine Really Protect Kids? (Time)

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Does the Flu Vaccine Really Protect Kids?

By Alice Park Monday, Oct. 06, 2008

Getting a flu shot is an annual rite of passage — or at least,

according to U.S. health officials, it should be. For the first time,

the Centers for Disease Control and Prevention (CDC) recommends this

year that all children aged six months through 18 years receive the

flu vaccine; previous advisories included children only up to five

years old.

Government data indicate that the flu shot is more necessary than

ever. The rate of flu deaths among children, while not high, are

continuing to rise — more than 80 deaths were recorded in the

2007-2008 flu season, according to the CDC — highlighting the

potential benefit of vaccination.

Yet a new study published Oct. 6 in the Archives of Pediatrics &

Adolescent Medicine suggests otherwise — that the flu shot in children

doesn't necessarily protect them from illness. Led by Dr.

Szilagyi, researchers at University of Rochester studied 414 children

aged 5 and younger, who came down with the flu during the 2003-2004 or

2004-2005 flu seasons. These children were compared with over 5,000

controls who did not have influenza during the same seasons. Turns out

that flu shots seemed not to make much difference: Kids who got

immunized did not get the flu at lower rates than unvaccinated kids.

In fact, the immunized youngsters were just as likely to be

hospitalized or to visit the doctor as kids who never received the

vaccine.

But before you decide to skip the flu shot this year, experts warn

that results of flu studies like this are all about design. Depending

on how a particular trial is set up — which populations are studied,

which vaccine is used and how many subjects are included — the results

can vary, and quite significantly. The Rochester study, for example,

happened to look at the effectiveness of a vaccine during two seasons

in which the flu strain included in the vaccine was not well matched

to the predominant circulating strain that was making people sick.

That could explain the lack of protection among the vaccinees — the

shot may have been protecting against the wrong flu proteins.

Targeting the correct strain is a always a bit of a guessing game,

however; researchers make their best scientifically based prediction

as to which flu virus will be making the rounds in a coming season,

but they often have to make these predictions up to nine months ahead

of time, in order to keep up with the lengthy vaccine manufacturing

process. " In some circumstances, it is like forecasting the weather, "

says Dr. Geoffrey Weinberg, professor of pediatrics at University of

Rochester. " Sometimes we are right on, and sometimes we are off. "

Another reason for the flu shot's failure may have been the fact that

certain forms of the vaccine are more effective than others in

children. In this study, most of the children received the injected

vaccine, but recent studies have shown that the nasal spray, known as

FluMist, appears to be better at protecting youngsters from influenza

(offering about the same level of protection as the injected vaccine

in adults). In kids, says Dr. Schaffner of Vanderbilt

University School of Medicine and an advisory member of the CDC's

Advisory Committee on Immunization Practices, the nasal spray may help

the immune system launch a broader and more diverse immune defense,

since the vaccine contains weakened forms of live flu virus that

replicate rapidly in the mucosal tissues. Such furiously multiplying

viruses may actually benefit vaccine effectiveness in flu seasons like

those included in the study, when there is significant mismatch — or

" drift " — between the circulating flu strains and the vaccine strains,

because the faster the viruses divide, the more likely they are to

develop more mutations, some of which may actually end up matching

those circulating in the community.

Finally, notes Weinberg, who was not involved in the new study but is

familiar with its design and results, the lack of effectiveness could

have been due in part to the trial's small sample size. " The bigger

numbers you have, the better, " he says. " Five hundred subjects may

sound like a lot, but once you start stratifying them by age, by

whether they received all of their shots, or which year they were

immunized, your total number gets smaller. "

All of which means that, as this study's results show, we need to

become more realistic when it comes to our expectations of the annual

flu shot. There is no guarantee that it will work, but on a population

level, odds are that it's better to get a flu shot than not. " We all

recognize that the influenza vaccine is not as effective as the polio

vaccine, or the measles vaccine, " says Schaffner. " It's not a great

vaccine, but it is quite a good vaccine. We are not going to eliminate

influenza through the use of this vaccine. But we can mitigate its

devastating impact on the population if we get immunized. "

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