If you haven’t been vaccinated yet this flu season, here’s what you need to know.

Flu activity is picking up across the country, with widespread infection in 24 states, according to the CDC. If that news has you worried about your own chances of coming down with the virus, here’s a major step you can take to protect yourself (if you haven’t already): Go get a flu shot.

That’s right. No matter what your reason was for putting off your flu vaccine, there’s still time to get one, even if it is January already. Here’s why.

What does the flu shot do?

Getting the flu shot causes your body to produce antibodies that fight the flu. These proteins in the blood are part of the immune system’s natural response to potentially harmful invaders. The vaccine makes it so that if and when you come in contact with one or more of the viruses that cause the flu, you’re less likely to develop flu symptoms.

How effective is the flu shot?

This year, the strain of the flu that seems to be most prevalent is influenza A in the form of H1N1. During last year’s particularly brutal flu season, H3N2 was the dominant strain, and the CDC estimated the flu shot was effective around 30% of the time. Why does the vaccine’s effectiveness vary from year to year? Before every flu season, health experts tweak the ingredients in that year’s flu vaccine, hoping to make it as effective as possible in protecting against the particular strains of flu-causing viruses that are expected to emerge. If that sounds tricky, that’s because it is.

“We need more research so we can develop an influenza vaccine that works 100% of the time, for 100% of people,” says Pritish K. Tosh, MD, a Mayo Clinic infectious disease physician and researcher. “But we do have a vaccine that is effective in preventing influenza infection and also, in those who get infected, in preventing complications such as hospitalization and even death. While the research is ongoing to create a better vaccine, we need to use the one that we already have.”

So, is it too late to get the flu shot?

Not at all. Flu season peaks from December to February, but it can last until May, according to the CDC. “If somebody hasn’t gotten infected yet, there’s still time to get infected. Therefore, getting the vaccine may help prevent infection and serious complications,” Dr. Tosh says.

In an ideal world, everyone would be vaccinated early in the season. It takes about two weeks for the flu shot to become effective, so the CDC recommends getting your flu shot by the end of October. That way, you’re fully protected by the time flu activity picks up, but not before. “The immunity generated does wane, so there is some thought that if you get it too early, perhaps by the end of the season you’re not getting the full effect,” explains Richard Webby, PhD, a member of the infectious diseases department at St. Jude Children’s Research Hospital.

Even after influenza A circulation slows, other strains, like influenza B, may circulate later in the winter. “It’s not atypical [for] an early influenza A season to be followed by smaller but later influenza B activity,” Webby says. The flu shot also protects against influenza B and, as in years past, pretty effectively, Dr. Tosh adds.

Where to get the flu shot

If you haven’t been vaccinated yet and you’re finally convinced that it’s time, you may contact at one of our clinics (Vistasol Medical Group or Morelia Clinic) as soon as possible to schedule an appointment for your FLU shot.