WEDNESDAY, Dec. 23, 2015 (HealthDay News) -- Although relatively few cases of flu have surfaced so far in the United States, health officials expect activity to pick up in the next few weeks, so everyone who hasn't gotten a flu shot should get one now.
"So far, influenza activity this season has remained low," said Lynnette Brammer, an epidemiologist in the influenza division at the U.S. Centers for Disease Control and Prevention.
"We are seeing a mix of flu strains, but activity is still low, so it's a great time to go out and get vaccinated if you haven't yet," she said.
This year's slow start to the flu season isn't unusual, Brammer said. "It feels a bit unusual because the last three years were early years, but this is sort of typical," she explained. "The majority of flu seasons peak in February."
Brammer expects flu activity to pick up in the next few weeks. "It's possible that this year's flu season will be a mild one," she said. "But we just don't know."
According to the CDC, right now flu activity is high in South Carolina and moderate in Arizona, Mississippi and Texas. Flu levels in the rest of the country are low.
Even when flu is epidemic, it's not too late to get a flu shot, Brammer said. "But you get the most benefit if you get vaccinated before there is a lot of flu activity," she said. "The sooner, the better."
In a typical flu season, flu complications -- including pneumonia -- send more than 200,000 Americans to the hospital. Death rates linked to flu vary annually, but have gone as high as 49,000 deaths in a year, the CDC says.
Virtually everyone older than 6 months of age is advised to get a flu shot. The exceptions are people with life-threatening allergies to flu vaccine or any ingredient in the vaccine. This might include gelatin, antibiotics, or other ingredients, according to the CDC.
Pregnant women are at high risk and should get vaccinated. Women with newborns also need to get their flu shot to help protect their infants, who can't be vaccinated until they are at least 6 months old. Also at risk are seniors and people with chronic health problems, such as lung and heart disease.
How effective the vaccine is in preventing the flu depends on how good a match it is to the strains of flu virus circulating that year. Most years, the vaccine is between 40 and 60 percent effective, according to the CDC.
Last year, the vaccine offered little protection against the most common flu strain that circulated, an H3N2 virus, Brammer said.
That happened because the virus that experts predicted to be predominant wasn't, and the new H3N2 virus was not included in the vaccine, she explained.
This mismatch caused a severe flu season, especially for the very old and very young, and led to a record number of hospitalizations for flu among the elderly, according to the CDC.
This year's vaccine contains the new H3N2 strain, but it's too early to tell which strains will dominate, Brammer said. For example, the H3N2 strain was the most common strain earlier this season, but last week the H1N1 strain was the most common, she said.
That strain, however, is also included in the vaccine. "All the viruses we are seeing are in the vaccine," she said.
Based on what has happened so far, Brammer thinks this year's vaccine is a good match for the circulating flu viruses and is a better match than last year's shot.
Manufacturers are expected to produce 170 million to 180 million doses of flu vaccine this year. While plenty of vaccine is still available, Brammer said supplies may be dwindling, and in some areas of the country you may need to make a couple of calls to find the vaccine.
"But I haven't heard anything about distribution problems or supply problems," she said. "People shouldn't have a hard time getting vaccine."
Dr. Marc Siegel, an associate professor of medicine at NYU Langone Medical Center in New York City, said, "Everyone needs to get a flu shot, because it creates a ring of immunity that protects your pregnant wife or your young child or your elderly parent."
The more people who are vaccinated, the fewer people at risk, he said. In a year like this, when the vaccine appears to be a good match, one can expect close to a 70 percent decrease in urgent care visits from flu if one has been vaccinated, Siegel noted.
"This means fewer secondary infections like pneumonia, bronchitis, ear infections, fewer heart attacks brought on by flu, fewer hospitalizations and fewer deaths in those who have received the flu vaccine," he said.
For more on flu, visit the U.S. Centers for Disease Control and Prevention.