"We find it peculiar that the claims that influenza can prevent half or more of all winter deaths in elderly people have not been more vigorously debated," Simonsen wrote.

UC Davis' Siefkin and Sutter Roseville Medical Center infectious disease specialist Dr. Randy Martin counter that it's not necessarily the flu that leads to death or serious medical conditions; it's the secondary bacterial infections that develop after contracting the flu. And those data are hard for researchers to measure.

Mortality figures aside, the data suggest there is limited benefit in getting the shot as a means of warding off bouts of the flu.

The Cochrane Collaboration, an international organization that reviews research, looked at two dozen clinical trials on flu shots. It found that, among those who received the vaccine, 19 percent developed the flu. Among the control group, 23 percent.

One reason that flu shots often proved ineffective is that the World Health Organization has to work at least a year in advance – due to the time it takes to manufacture the vaccine – to figure out which strains will end up circulating in North America. The Mayo Clinic Health Letter reports the match has a 90 percent effectiveness.

But a study released Monday by the University of Rochester Medical Center reported that children are half as likely to get the flu even when the vaccine is considered a "poor match" to the strains.

"Last year's vaccine probably missed the target," Martin says. "People say the vaccine for this year looks like it's going to be right on target, but we'll have to see when the flu season hits (January, February)."

But that does not mean that the flu shot somehow "caused" a person to get sick. It could just be that the patient caught a strain of the flu not covered by the vaccine. (Certainly, people have had minor reactions directly as a result of the shot – soreness and redness at the injection site and a slight fever – but not classic flu symptoms.)

"People will get a virus two weeks after the injection and say, 'Doggone it, I'm not getting a flu shot anymore because it didn't protect me,' " Siefkin says. "But, no, you didn't get the flu. You got a cold that was bothersome."

Concern for kids

As skittish as adults are about getting the flu shot, parents of young children have the added concern about perceived side effects. Government figures show that only one in five children ages 6 months to 23 months and one in six for children 24 months to 5 years receive the injection.

Parents are concerned that some flu shots use the preservative thimerosal, which contains mercury. Though no studies have linked thimerosal to autism, many of the manufacturers have stopped using the preservative.

Djina Ariel, a certified nurse midwife at Woodland Healthcare, says she immunizes her children for diseases such as polio and pertussis (whooping cough). But for conditions such as the flu and chicken pox, "I just let them get sick for (the) immunity."

As for herself, "If I thought the flu would do more than just lay me low in bed for a few days I would probably get immunized."

Siefkin is much more adamant. He says doctors at UC Davis Medical Center recently agreed to get vaccinated to protect patients from flu. "If you can't convince people getting the shot is for their own health, try to convince them it's for others' health," Siefkin says.

Call The Bee's Sam McManis, (916) 321-1145.