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

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.