A September pediatric flu death in California serves as a stark reminder that getting vaccinated early can save lives.

Public-health officials in Riverside County, Calif. announced this week that a recently deceased 4-year-old child from Perris, who had underlying health issues, tested positive for influenza. The case is the county’s first pediatric flu-related death of the 2019-2020 flu season, according to a release. (The spread of flu typically picks up in October or November, and can last until May.)

While it may feel too early to think about the flu, the U.S. Centers for Disease Control and Prevention (CDC) said in its most recent flu vaccination recommendations that “vaccination should occur before onset of influenza activity in the community” to ensure the best protection against the virus. For most people, that means getting vaccinated by the end of October.

But parents may need to think about vaccinating their children even earlier. The CDC recommends that children ages six months to eight years, who require two doses of the flu vaccine, should get their first shot “as soon as possible after the vaccine becomes available,” since they must wait at least four weeks to get the second dose.

It’s also especially important that young children get vaccinated, since they are both particularly susceptible to serious flu complications, and more responsive to the vaccine than adults. Last year, 130 U.S. children died from the flu—and a recent CDC study found that the number of babies hospitalized for influenza is at least twice as high as current estimates suggest.

Flu vaccines are not perfect. Last year’s, for example, was only 37% effective against flu strains for adults, and 61% effective for kids, according to CDC estimates. Even still, the CDC recommends that everyone older than six months get a flu shot each year, unless they have medical conditions that make vaccination unsafe. Vaccination both reduces the risk that an individual will get sick, and lowers the chances of passing on the virus to others in the community—especially babies and those with compromised immune systems, who may not be able to get the shot themselves.

Write to Jamie Ducharme at jamie.ducharme@time.com.