The best time to get a flu shot

In the waning days of summer, flu season can still feel a long way off. Yet some pharmacy chains have already started urging consumers to beat the crowds and schedule a flu vaccine.

However, experts said that for most people, getting a shot at the start of September may be too early to provide protection that will last throughout flu season.

This year’s vaccines protect against several flu viruses, which can cause fever, fatigue, body aches, diarrhea, and other symptoms. In serious cases, an infection can lead to hospitalization or even be fatal. There were about 35 million cases of flu nationwide last season. About 400,000 people were hospitalized with flu infections, and 25,000 people died.

When is the right time for a shot?

Ideally, you want to get your flu shot before cases in your area start picking up. The problem is, it’s difficult to predict when exactly that will happen because it varies in different parts of the country and from year to year. The COVID-19 pandemic also disrupted flu season, delaying the start and sharply diminishing the spread of the flu virus from 2020 to 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 designated Oct. 5 as the start of its flu surveillance season.

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

Generally speaking, your immunity peaks a week or two after a flu shot. Even after it peaks, protection lasts five or six months. This is typically enough protection to get you through flu season, which tends to begin in October and end in March or April.

There are some exceptions to those recommendations. Experts said pregnant women in their third trimester should get vaccinated now to confer flu immunity on their newborns.

Some children between 6 months and 8 years old need two flu shots, four weeks apart. This includes children who have never gotten a flu shot, who have only received one dose or who have an unknown vaccination history. Experts say that for young children, an initial course of two doses provokes the best immune response to flu. Alicia Budd, the team lead of the influenza division at the CDC’s National Center for Immunization and Respiratory Diseases, said children who need two doses can get their first shot now.

If you miss your flu shot during the recommended window this fall, it’s still worth getting vaccinated, experts said: Protection late in the season is better than none at all.

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

Each year, the World Health Organization studies data from Australia and South America, where flu seasons start earlier, to help drugmakers tweak vaccines for better protection against the flu viruses likely to prevail in the United States.

This year, the vaccines available in the United States are formulated to protect against two influenza A viruses and one influenza B virus. (In previous years, flu vaccines targeted four viruses, but this year, drugmakers dropped one flu virus that largely disappeared during the pandemic.) Most of these are shots, given as an injection in the arm, but there is also a nasal spray flu vaccine. Experts said this might be a good option for eligible patients who are afraid of needles. There are specific high-dose vaccines for people 65 and older, who are at higher risk of severe illness.

An infection with flu will also generate some immunity — but only against the particular flu virus that made you sick. The vaccine offers a much broader form of protection.

Experts say that everyone benefits from a flu vaccine. Children, in particular, can spread the virus easily and are the most susceptible to infection. Children under 5, especially those with other medical conditions, are at risk of severe illness. Yet only 57% of children and adolescents received one or more doses of flu vaccine last season, according to CDC data.

“Year after year, we see that many of the children who die from flu are not immunized or are only partially immunized,” said Dr. Kristina Bryant, a pediatric infectious diseases physician at Norton Children’s in Kentucky. “I think people forget that this is not just a cold.”

This article originally appeared in The New York Times.