The vaccine for influenza is available now in pharmacies, but you might be wondering when you should get it and how to time it with a COVID-19 vaccine or booster shot.

Dr. Timothy Friel, chair of the Department of Medicine Infectious Disease at Lehigh Valley Health Network, provides some guidance.

Friel said the flu season usually starts as early as November and can last to as late as May. He recommends not getting the flu shot too early in the season, because if the season peaks late then the person’s immunity will be waning.

“There’s a bit of a guessing game in all of this. I think the ideal time is the beginning of October to very, very early November,” he said about when to get the flu shot. “That tends to have you covered for the most common months that we experience influenza.”

People of all ages are encouraged to get the influenza vaccine. Children as young as six months can get a flu shot.

The flu vaccine is created with inactivated parts of the virus. It takes seven to 14 days to get optimal protection from the flu. Protection lasts for about six months.

There is also a nasal spray flu vaccine for people between the ages of 2 and 49 years old. This vaccine is created with a weakened live flu virus.

Friel said four flu viruses are targeted this year by the vaccine, which is why it’s called a quadrivalent vaccine.

“We do our best, based upon looking at what’s happening in the southern hemisphere, to try to predict what will happen in the northern hemisphere where we live during our winter months,” he said.

Safety measures like mask wearing and social distancing have prevented the spread of the flu, too, so it has been harder than usual to know which flu viruses to target.

Although the flu vaccines are not created using the mRNA construct like the COVID-19 vaccine, this could change.

Friel said researchers are using the mRNA platform for the influenza vaccine and have started some clinical trials. They want to increase the efficacy of the flu vaccine.

Currently, the COVID-19 vaccine booster shot has not been approved by the Food and Drug Administration for use in the general population. Booster shots are available for people who are immunocompromised.

An FDA advisory group is expected to meet on Friday to discuss the date. If approved for the general population, booster shots could become available as early as Sept. 20.

An article in The Lancet, a medical peer-reviewed journal, reported on Monday that a booster shot may not be needed yet. A panel including two senior officials from the FDA said that the data shows that the efficacy lessens over time in preventing mild illness, but continues to have protection against severe disease symptoms.

According to the Centers for Disease Control and Prevention, more than 176 million people are now fully vaccinated for COVID-19 in the United States, as of Sept. 7.

Of those people, 14,115 have had breakthrough cases. The majority of the people with breakthrough cases, who were hospitalized or died from the virus, were 65 years old or older - 2,331 people died, 7,954 were hospitalized.

Friel said it’s important to remember that the original goal of the vaccine for SARS-CoV-2 was “to prevent serious illness and death, the disease that puts people in a hospital. The disease that allows people or necessitates that they get care in an ICU, that they require intubation and ultimately the disease that can kill people. In that area, even with the delta variant, we’ve seen the vaccines hold up, and hold up really, really, really well, so we are still talking about efficacies in preventing serious disease, hospitalization and death in the mid to high 90s.”

Another key component to immunity are the T-cells or cellular immunity, Friel said. The cellular immunity helps to control the antibody-based immunity. Exposure to the disease stimulates the antibodies, so it’s a complex issue.

If the booster shot does get FDA approval, people can get it and their flu shot during the same pharmacy visit. Similarly, people just getting the COVID-19 vaccine now can also get a flu shot.

Friel said that the medical community recommended getting the flu shot at least two weeks before or after the COVID vaccine, out of an abundance of caution.

“Since that time, we’ve gained increased confidence and a better understanding of how vaccines interact, or in this case don’t interact,” he said. The two-week spacing is no longer applicable.