Dayton, Ohio -- Health officials haven't even begun actively monitoring flu cases, but they are advising residents to get vaccinated as soon as possible to protect themselves before the flu season kicks in to high gear.

The flu season can start as early as late September and last through May, and pharmacies, doctor's offices, and hospitals have already made the flu shot available.

"We've already had a handful of people come in to get vaccinated," said Kindy Ghussin, owner of Heartland Pharmacy in Kettering, Ohio. "There's no appointment needed. You can walk in and get it anytime."

One reason to get the vaccine early is to avoid shortages that might occur during seasonal outbreaks. But health officials say such shortages are unlikely this year.

"There is plenty of vaccine to go around," said Dr. Mary DiOrio, medical director for the Ohio Department of Health, who noted manufacturers have projected they will provide between 171 million and 179 million doses of vaccine for the U.S. market this season.

DiOrio said the main reason to get the flu shot early is that it takes about two weeks after getting the vaccine for antibodies to develop in the body and provide protection.

"We'll start monitoring (flu cases) actively at the beginning of October because that's usually when your flu season starts," she said. "Flu is unpredictable, and we'll just have to see what happens."

Clark County (Ohio) Combined Health District Epidemiologist Gabe Jones said he was concerned about the emergence of the flu in other parts of the state over the summer.

"Outside of the October-May time frame, if you get a case of the flu, it's pretty unusual," Jones said. "The last time we saw that happen was with the novel flu."

Jones was referring to the 2009-2010 flu season when Ohio was among a majority of states hit by a novel strain of the influenza A/H1N1 virus, commonly referred to as "swine flu."

"We'll have to wait and see what happens during the flu season to see if we get any new viruses," DiOrio said. "We are looking for those variant viruses, but right now the ones that we're seeing are human strain viruses."

DiOrio said this year's flu shot should be effective against the most common flu strains. One shot contains two A strains -- considered the most severe flu virus -- and one B strain. Another shot has two of each, otherwise known as a quadrivalent vaccine because it protects against four different types of flu virus.

"The vaccine this year will cover different strains of flu than the one last year," DiOrio said. "We're optimistic that it's going to be a good match."

More people tested positive for the flu during the 2014-15 season than the previous season, in part, because last year's flu shot was only about 13 percent effective, according to the Centers for Disease Control and Prevention.

Last year's vaccine didn't fully protect against a mutated strain that emerged after the flu season started.

This season's vaccine contains the mutated H3N2 strain as well as other strains expected to dominate this winter and should be 50 percent to 60 percent effective, as it is in most years, the CDC said.

The CDC recommends everyone 6 months or older get the vaccine annually.