Two physicians who lost their young son to the flu last year want parents to listen to their message, born of great grief and suffering: Get your child a flu shot.
Drs. Laura and Anthony Sidari's 4-year-old son, Leon, did not get the flu vaccine last year. He died on Christmas Day, less than 48 hours after he started feeling sick.
"I didn't know a condition could kill a child that quickly who had been previously healthy," said Laura, a psychiatrist. "This has been a hard haul for us, and we're very private people, but we're trying to help other families."
Leon was one of 180 US children who died in the 2017-18 flu season, according to the Centers for Disease Control and Prevention -- a historic high.
Approximately 80% of those children had not received a flu shot, according to the CDC.
Laura and Anthony, a rheumatologist, had wanted to get Leon and his 2-year-old brother flu shots at a pharmacy. They lived in Texas, where state law prohibits pharmacists from vaccinating anyone under the age of 7.
The couple, busy with their newborn third child, Cameron, decided to get Leon a flu shot when they were going to the pediatrician anyway: when 2-year-old Tristan had his annual visit, scheduled for January 3.
Leon died 10 days before that appointment.
"It wasn't even on my radar as something that I really, really needed to prioritize," Laura said. "It just slipped through the cracks."
The Sidaris' story is all too familiar to Dr. Flor Muñoz.
For 20 years, Muñoz, a pediatric infectious disease specialist at Texas Children's Hospital, has worked with the American Academy of Pediatrics to increase the rate of flu vaccination for children.
The rates aren't great: Only 47.8% of children 6 months to 17 years old have had a flu shot in the previous year, according to the CDC, which recommends that everyone over 6 months get a flu shot.
The problem: Though adults can get flu shots at pharmacies or even at work, children don't have as many options.
In most states, there are limits or outright bans on pharmacists vaccinating children, and flu vaccine clinics at schools are the exception rather than the rule.
Only 13 states allow pharmacists to vaccinate children of any age, according to the National Association of State Pharmacy Associations.
"It's frustrating. It seems like we don't learn," Muñoz said.
There's no medical reason children shouldn't get flu shots at a pharmacy, said Muñoz, who is also an associate professor of pediatrics at Baylor College of Medicine.
Some states are changing their laws. New York used to bar pharmacists from giving flu shots to anyone under 18. This year, after the historic flu season, the state changed its laws to permit vaccination for anyone 2 or older.
"Good for you, New York!" Muñoz said. "More should be done to make this happen in other states. There should be more of a push."
Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center, said more should also be done to make it easier for local health departments to offer flu shot clinics. Right now, he said, it's difficult for those departments to purchase large quantities of vaccine and to bill insurance.
"We need to do more to make it easy," he said.
The Sidaris are doing their part. Last month, they sponsored a "Say Boo to the Flu" event in their hometown, Albion, New York, where 59 children were vaccinated.
Although the CDC encourages flu vaccines by the end of October each year, it's especially important to get the shot well before the holidays, Muñoz said. Flu activity can peak in December, and holiday get-togethers can make the virus spread more quickly. It takes about two weeks for the shot to become effective after you receive it.
"Leon is my reason this season, and every season, for getting flu shots on time," Laura Sidari wrote on her Facebook page. "Holiday planning and fall festivities can wait, but the flu shot cannot."
CNN's John Bonifield contributed to this story.