(CNN) - Most US adults have not gotten a flu shot this season, according to a new survey from NORC, a research organization at the University of Chicago.
As of mid-November, only 43% of surveyed people 18 or older said they had gotten vaccinated against the flu, according to NORC, which has conducted the National Immunization Survey for the US Centers for Disease Control and Prevention since 2005. Another 14% who remain unvaccinated claim that they will get the shot, the survey indicates.
Even if they do as they intend, that leaves considerably more than a third of adults (41%) who have not -- and will not -- get a flu shot, according to NORC. (The remaining 2% either did not answer or responded, "I don't know.")
The report comes early in what has been a mild season. Thirty-eight states, the District of Columbia and Puerto Rico experienced minimal flu activity for the week ending December 1, while New York City and 10 states experienced low or moderate activity, according to Friday's weekly flu report from the CDC. Only two states, Georgia and Louisiana, experienced high activity during the week.
The mild season is a dramatic shift from the previous flu season, which was the deadliest in decades, with more than 80,000 flu-related deaths in the United States.
'It's still very, very early'
"We cannot claim that the 43% of vaccinated people is the reason for the mild flu season so far," said Richard Webby, a flu scientist and adviser to the World Health Organization on recommendations for the composition of flu vaccines. Webby, who was not involved in the NORC survey, said vaccination rates are similar to those of years in which flu activity has been widespread and illness severe for many people.
"We've got to keep in mind that it's still very, very early, and even at this time last year, there hadn't been a huge amount of activity either," said Webby, a member of St. Jude Children's Research Hospital's Department of Infectious Diseases.
No children died as a result of the flu during the week ended December 1, though five children died earlier this season, the CDC reported. Among adults, flu deaths are estimated based on pneumonia and other illnesses related to flu. The proportion of deaths attributed to pneumonia and flu was below the usual threshold for this time of year, the CDC said.
Among those who visited a doctor's office, just 2.2% said the reason for their visit was flu-like illness; this is considered a normal rate for this time of year, according to the CDC.
The report also showed a total of 383 hospitalizations reported since October 1, with slightly more than 1 flu-related hospitalization for every 100,000 people during the week ended December 1. The highest rates of hospitalization were among adults 65 or older and children younger than 4; both age groups saw slightly more than 3 flu-related hospitalizations per 100,000 people.
Webby said a "slightly reassuring signal" this year is that the H1N1 strain is the dominant strain of flu circulating.
"That's the strain that's a little bit better match to our vaccine," he said. "It tends not to have quite the same impact that the H3N2 season does, and that's what we had last year." Influenza B strain viruses, which have the same symptoms as A-strain viruses, are also circulating this season as usual, the CDC said.
There were 1,105 new laboratory-confirmed cases during the week ending December 1, bringing the season total to 6,170, the CDC calculated. These numbers do not include all people infected with the flu, because many people do not seek medical help when they are sick and so go uncounted.
Why you should consider getting a flu shot
The most important response to seasonal flu, according to the CDC, is for everyone 6 months or older to get vaccinated. As long as flu is circulating in the area where you live, it is not too late to get vaccinated.
Looking at the new NORC report, Webby worries about "the quarter of people [age] 60-plus that are not getting vaccinated." Adults over 65, children under 2 and individuals with medical conditions not only should get a flu shot, they should get a pneumococcal vaccination to prevent pneumonia, according to the CDC. Flu is more likely to be severe or even deadly in these groups than among healthy adults.
About half the people in the 18- to-44 age group also haven't gotten a flu shot, noted Webby, who believes that "it's probably an uphill battle" trying to increase these vaccination rates. After all, flu infections don't usually cause severe illness in this age group.
"We're struggling a little bit by the perception that flu is not really a deadly disease, which of course we know it is," he said. "Perhaps the healthy adults are at a fairly small risk of getting a very very severe flu infection, but if they do get infected, they're potentially still infecting others. And how many people in that age group have young kids or have elderly parents?"
Young children and the elderly are at higher risk of getting severe illness, Webby said: "So by getting vaccinated, you're not just protecting yourself, but also, through herd immunity, you're protecting others."
The overall effectiveness of last year's flu shot was estimated to be 40%, meaning vaccination reduced an individual's risk of seeking medical care by 40%, according to the CDC. Among children, effectiveness rates were higher: Children who got the shot were 59% seek medical care for the virus, the CDC reported this year.
Though the vaccine is imperfect, it lessens the severity and duration of symptoms, and those who get flu after receiving a vaccine are less likely to require hospitalization and less likely to die.
Webby added that the vaccine is also safe. Though some people report a sore arm after getting the shot, the overwhelming majority experience no extreme side effects.
"The vaccine has been given to many people every year with a very good safety record," he said.
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