Too soon for the flu?
Experts agree that influenza can be deadly and getting vaccinated is critical. But when?
Each year a flu vaccine is designed by a experts who try to identify the strains most likely to spread across the U.S. (Chuck Berman, Chicago Tribune)
The answer to that question depends on whom you ask.
The sign in the pharmacy window might suggest flu season is already here, and the Centers for Disease Control and Prevention is urging everyone at least 6 months old to get a dose of prevention "as soon as possible."
But according to some infectious disease experts, the beneficial effects of a flu shot received in August or September could start to fade just as the virus kicks into high gear.
While doctors can never predict exactly when it will strike, the official start of flu season has long been October, with the number of cases typically peaking in February or even later.
Medical professionals agree that a flu vaccine loses its potency over time, a phenomenon called "waning immunity." What they don't agree on is how long the vaccine can be expected to protect a person against particular strains of the virus.
"Getting the vaccine early beats not getting the vaccine at all," said Dr. Jorge Parada, director of infection control and prevention at Loyola University Health System. "But if you get it very early, you may have your waning immunity in February, which is peak flu season. I personally see no reason to get the vaccine until October."
But to keep pace with other providers, Loyola officials decided to begin offering influenza vaccinations to patients earlier this September. The hospital is waiting to vaccinate its employees, however, until October.
"There are two sides of the coin," said Dr. Michael Jhung of the CDC's influenza division in Atlanta. "Do you vaccinate now and have that be too early … or do you wait, and find out that is too late? (If) you wait too long, you might not need the vaccine because you've already got the flu."
Influenza is a highly contagious virus that attacks the upper respiratory system. While still viewed by many as a routine part of winter, only moderately more punishing than the common cold, the flu causes 3,000 to about 49,000 deaths in the U.S. each year, according to the CDC, which based its estimate on numbers gathered between 1976 and 2007. The agency notes the "variability and unpredictability of flu" in making its estimate.
Each year, a vaccine is engineered to protect against three different strains of flu. Experts try to identify the strains most likely to spread across the U.S. They typically zero in on strains active in the Southern Hemisphere, where countries experience winter when it is summer in the Northern Hemisphere.
"Sometimes they are spot-on, and the vaccine is very effective … and sometimes they miss," Parada said.
Last year, the seasonal flu arrived later than usual, peaking around March, and the toll it took in the U.S. was relatively mild, according to the CDC.
While the flu changes year to year, the predominant strains of the virus in the 2011-12 season were the exact same as those targeted the year before. But flu strains most likely to crop up this season are different from last year, officials say.
This year's vaccine includes a strain of the influenza A virus, which is capable of major mutations, and a strain of the influenza B virus, which mutates just enough to make people sick year after year. The cocktail also includes the same H1N1 virus first discovered in pigs in 2009.
The secret to preventing the spread of influenza, as well as some other contagious diseases, is something called "herd immunity." According to doctors, when enough people in a community are immunized, the chances for an outbreak become slim, and even those who fail to get a flu shot are protected.
"The main thing is to remind people early," said Dr. Lisa Grohskopf, medical officer in the CDC's influenza division. "(The timing) is not something we can predict with absolute certainty. That makes it difficult for us to tell people to wait."
More people have been getting influenza inoculations than at any time in the past, the CDC reports. In addition to a shot, the vaccine can be administered through a mist.
When the agency issued its first influenza advisories in the 1960s, the flu shot was recommended only for people 65 or older and those suffering from chronic diseases. That's the way it stayed until 2000, when the agency decided that healthy adults as young as 50 also should be inoculated.