The months from October to April are considered the peak of flu season, and New Jersey health officials urge everyone older than 6 months to get vaccinated for influenza by the end of October.

Robert Giroux, Getty Images News

"The reason why we recommend as early as possible is because the flu season is so unpredictable and you don't know how early flu might rear its ugly head," State Epidemiologist Tina Tan told Townsquare Media. "The earlier that you can get vaccinated, the earlier you'll get protection against the flu virus in general."

Following a vaccination, it takes the body about two weeks to build protection against influenza virus infection.

While no vaccine is 100 percent effective, the performance of a flu vaccine can also decrease over time, Tan noted.

A vaccination's level of protection can vary based on a person's immune system and depends on how well the vaccine matches the flu viruses circulating in the community.

Vaccinations tend to differ from year to year based on which viruses are expected to pose the biggest threat to the public. That's why vaccines are recommended annually.

A mutation of the virus during the 2014-15 flu season resulted in a 20 percent efficacy rate for the vaccine. Last year's numbers were a stark improvement.

In 2015, the influenza activity level was considered "high" in New Jersey through the week ending April 2, but flu season got off to a slow start.

Sign up for the WPG Talk Radio 104.1 Newsletter

Get South Jersey news and information e-mailed to you every week.