This year’s flu season is looking like a bad one, with more people visiting the doctor for flu symptoms now than at any point last season.

And yesterday (Jan. 9), Boston declared a public health emergency after its state reported 18 flu-related deaths.

The best way to protect yourself against the flu is to get the flu shot, and the best time for that is before the flu season starts. But what if you put it off until now? Here are some answers to common flu shot questions:

Is it too late to get the shot?

No, it’s not too late to get a flu shot, said Randy Wexler, a professor of family medicine at Ohio State University. Typically, flu season lasts until March, so there’s still a benefit to getting the shot now, Wexler said.

Just get it as soon as possible, health experts say.

Is the shot widely available now?

Enough vaccine has been produced so that people who want a shot now should be able to get one, Michael Jhung, a flu expert at the CDC, told USA today. People may experience delays and need to visit more than one pharmacy, but should not be discouraged, Jhung said.

Wexler said he has not heard of people having problems getting a flu shot, and there has not been a shortage of the flu vaccine this year.

How long does it take immunity to kick in and how can I protect myself from catching the flu until it does?

After you’ve had your shot, it takes about two weeks for immunity against the flu virus to develop. Frequent hand washing is important to protect against the flu, Wexler said. [See How to Avoid Spreading the Flu.]

How effective is this year’s flu vaccine?

The effectiveness of the yearly flu vaccine depends upon several factors, including how well the flu strains in the vaccine match the strains in circulation. Some studies show that when strains in the vaccine are a good match with the ones that are circulating , vaccinated individuals are 50 to 60 percent less likely to catch the flu than people who aren’t vaccinated.

This season, about 90 percent of the flu strains in circulation that have been analyzed at CDC are a good match to viruses included in the 2012 to 2013 influenza vaccine.

Can you get the flu even if you’ve had the flu vaccine?

Yes. The CDC has received reports of some people who were vaccinated with this year’s flu shot who later got the flu. This happens every season, the CDC says, and there are several reason it can occur:

  • People who got the flu may have been exposed to the virus prior to receiving shot, or within two weeks of getting it, before they had a chance to build up immunity.
  • They may have been exposed to a strain of flu virus that is not in the vaccine.
  • Not everyone responds the same way to vaccination, and some people, such as those with chronic illnesses, may not develop adequate immune protection after being vaccinated.

The CDC says it is not possible to tell at this point whether a higher number of people than usual are developing the flu after being vaccinated.

Can you get the shot if you have a cold? Why not?

Yes, as long as you don’t have severe symptoms, such as a fever. People who have a fever may have a reaction to the vaccine that will worsen their symptoms, Wexler said.

Should you get a flu shot if you’ve already had the flu (or think you had it)?

If you already had the flu, a flu shot likely won’t do you any good, Wexler said.

“If you’ve had the flu this year, it’s like you’ve immunized yourself against the flu,” Wexler said. But you should be sure that the illness you had was the flu, Wexler said.)

In addition, people who’ve had the flu this year should still get a shot next year, because the flu strains in circulation change from year to year year, Wexler said.

If I get the flu, can I take medication to stop it in its tracks?

The flu can be treated with antiviral drugs, sold as Tamiflu or Relenza. If started early, within 48 hours of the first signs of flu, the drugs can lessen symptoms and reduce the duration of illness by one to two days, the CDC says. The drugs can also prevent complications of flu, such as pneumonia.

The CDC recommends antiviral medications for people who are very ill with the flu, for instance, those who are hospitalized,  or people who have the flu and are at high risk for serious flu-related complications. High-risk individuals include young children, people ages 65 and older, people with certain underlying medical conditions and pregnant women.

Pass it on: It’s not too late to get your flu shot.

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