Youngsters 5 to 17 years old need to get vaccinated against influenza as soon as possible. That’s the main conclusion in a study in Morbidity and Mortality Weekly Report (MMWR) in which researchers found that that age group—particularly children 5 and under—had been particularly hard-hit by last year’s flu.
In the 2022-23 flu season, children younger than 5 years old experienced their second highest rates of medical visits and hospitalizations due to flu since 2016-17 (11,443 per 100,000 and 119 per 100,000, respectively).
“National estimates of the rates of influenza-associated medical visits and hospitalizations were higher than those during most previous seasons for children [younger than 5 years old] and children and adolescents aged 5–17 years,” the study states. “This high incidence strained health care systems, particularly with the co-circulation of SARS-CoV-2 and RSV.”
For the current 2023-23 flu season, the Centers for Disease Control and Prevention (CDC) recommends that for children 6 months through 8 years, the number of doses needed should be based on the child’s age when given the first dose of the 2023-24 flu vaccine as well as the number of doses of flu vaccine the child received in previous seasons.
Children in that age group who received two total doses or more of the of the trivalent or quadrivalent influenza vaccine four or more weeks apart before July 1, 2023, need one dose of the 2023-24 flu vaccine. Children in that age group who haven’t received two or more doses of the trivalent or quadrivalent influenza vaccine four or more weeks apart before July 1, 2023, or whose flu vaccination history is not known, need to get two doses of 2023-24 vaccine given four or more weeks apart.
A protracted flu season in the U.S. can run from October to May, with peaks that vary from year to year, according to the CDC, which publishes MMWR. Though researchers could establish no direct link, they did find that vaccination rates for that age group had sunk to historic lows last year. The study states that the “findings underscore the importance of children and adolescents receiving a seasonal influenza vaccination, ideally by the end of October, and prompt influenza antiviral treatment for those who are hospitalized.”
They found that only 18.3% of youngsters 5 to 17 years old who’d been hospitalized for flu last flu season had been vaccinated by the third week of November 2022 compared with 35.8% to 41.8% in 2016-17 through 2021-22.
CDC researchers mined data from the Outpatient Influenza-like Illness Surveillance Network, the Influenza Hospitalization Surveillance Network and the National Vital Statistics System death registry.
Outpatient visits for influenza-like illness (fever plus cough or sore throat) was one of three severity indicators that researchers looked at; the other two being rates of laboratory-confirmed flu and the percentage of all deaths.
“The 2022–23 influenza season was classified as high severity among children and adolescents, the fourth season with that classification since the 2009 influenza A(H1N1) pandemic,” the study states. “Further, all three severity indicators not only surpassed intensity levels for high severity, but the peaks also occurred early in the season (late November and early December).”
The weekly percentage of outpatient visits for influenza-like illness, hospitalizations associated with the flu and the percentage of deaths due to the flu peaked between the 90th and 98th percentile, according to the study.
Outpatient visits and hospitalizations peaked in late November 2022, three weeks before the peaks in deaths, which remained elevated throughout December.
“The combination of low influenza vaccine coverage early in the season and unusually early influenza activity (57.1% of the season’s pediatric hospitalizations occurred by the end of November) likely contributed to the high observed rate of influenza-associated hospitalization, despite the moderately strong protection from the 2022–23 influenza vaccine,” the study states.