When is the best time to get vaccinated against flu?

As summer winds down, flu season may still seem a long way off. But some pharmacy chains have already begun urging consumers to get ahead of the crowds and schedule a flu shot.

But experts say that for most people, getting vaccinated in early September may be too early to provide enough protection for the entire flu season.

This year’s vaccines protect against several different flu viruses that can cause fever, fatigue, body aches, diarrhea and other symptoms. In severe cases, the infection can lead to hospitalization or even death. Last season, there were about 35 million cases of flu nationwide. About 400,000 people were hospitalized with flu infections, and 25,000 people died.

When is the right time to get an injection?

Ideally, you should get vaccinated against the flu before cases start to appear in your area. The problem is that it’s demanding to predict exactly when that will be, as it varies by part of the country and year. The Covid-19 pandemic has also disrupted the flu season, delaying the onset and significantly reducing the spread of the flu virus in 2020-2022.

Flu season started to return to normal last year, said Deepta Bhattacharya, a professor of immunobiology at the University of Arizona. This year, the Centers for Disease Control and Prevention has set Oct. 5 as the start of the season.

Experts say most people should get vaccinated between mid-September and overdue October. The CDC recommends getting vaccinated by the end of October at the latest.

Generally, immunity peaks a week or two after a flu shot. Even after it peaks, protection lasts for five or six months. That’s usually enough protection to get you through the flu season, which usually starts in October and ends in March or April.

There are some exceptions to these recommendations. Experts say pregnant women in their third trimester should get vaccinated now to provide flu immunity to their newborns.

Some children ages 6 months to 8 years need two flu shots, spaced four weeks apart. This includes children who have never received a flu shot, have only received one dose or have an unknown vaccination history. Experts say that in teenage children, the first two-dose series produces the best immune response to the flu. Alicia Budd, flu team leader at the CDC’s National Center for Immunization and Respiratory Diseases, said children who need two doses can get their first dose now.

Experts say that even if you miss the flu shot at the recommended time this fall, it’s still worth getting vaccinated: protection at the end of the season is better than none at all.

What does the vaccine protect against and who should get it?

The World Health Organization analyzes data each year from Australia and South America, where flu seasons start earlier, to lend a hand drugmakers improve vaccines to provide better protection against the flu viruses that are expected to be prevalent in the United States.

This year, the vaccines available in the United States are designed to protect against two influenza A viruses and one influenza B virus. (In previous years, flu vaccines targeted four viruses, but this year, drugmakers withdrew one flu virus that largely disappeared during the pandemic.) Most are injections given as a shot in the arm, but there is also a flu vaccine that comes in the form of a nasal spray. Experts say that may be a good option for eligible patients who are afraid of needles. There are special high-dose vaccines for people aged 65 and older who are at higher risk of severe disease.

Having the flu will also create some immunity—but only against the specific flu virus that made you diseased. A vaccine offers a much broader form of protection.

Experts say the flu vaccine benefits everyone. Children in particular can easily spread the virus and are most susceptible to infection. Children under 5, especially those with underlying health conditions, are at risk for severe illness. But only 57 percent of children and teens received one or more doses of the flu vaccine last season, according to CDC data.

“We see year after year that many children who die from the flu are unvaccinated or only partially vaccinated,” said Dr. Kristina Bryant, an infectious disease pediatrician at Norton Children’s in Kentucky. “I think people forget that this is not the common icy.”