AMARILLO, Texas (KAMR/KCIT) — With winter upon us, hospitals are beginning to see more children coming in with influenza. The Center for Disease Control and Prevention conducted a study during the 2019-2020 season to evaluate the effectiveness of vaccines against life-threatening influenza in US children.

Based on the data collected by experts, although vaccine-mismatched influenza was dominate, the vaccination significantly reduced the risk of critical and life-threatening influenza illness in children.

According to the study, children aged 18 years and younger who were admitted to the intensive care unit with acute respiratory infection across 17 hospitals, had “respiratory specimens” tested for influenza viruses and different strains of influenza.

The effectiveness of the vaccine was compared in test-positive versus test-negative cases, considering age, virus type, and severity. Life-threatening influenza included death or invasive mechanical ventilation, vasopressors, cardiopulmonary resuscitation, dialysis, or extracorporeal membrane oxygenation.

The study detailed that results were determined by enrolling 159 (70%, aged 8 years and younger) critically ill influenza case-patients and 132 (69%, aged 8 years and younger) controlled patients. Among the 56 controls, 29 (52%) were vaccine-mismatched, meaning the dosage given was not a match to the virus strain that was present in the patient, while 23 (41%) were vaccine-matched to the virus strain.

In addition, research was done on control patients with B-lineage viruses, with 30 of the 31 patients given a vaccine-mismatch, resulting in a 63% effectiveness against critical influenza, 75% against life-threatening influenza, and 57% against non-life-threatening influenza in children aged 8 years and younger.

According to information from the study, influenza accounts for a worldwide estimated 870,000 hospitalizations and 34,800 deaths annually in children younger than 5, with the US Advisory Committee on Immunization Practices (ACIP) recommending annual vaccination for all children since 2010.

The study was conducted in the 2019-2020 season as the concern about the vaccine failure due to the circulation of two vaccine-mismatched strains was raised, and because the B-lineage virus caused the largest national influenza epidemic in children since 1992, the study stated.

Additionally studies were conducted with children aged 6 months to 17 years by comparing the vaccination results between case patients who tested positive versus patients with influenza symptoms (controls), who tested negative for influenza.

“Respiratory specimens” were taken from the patients to determine who was positive for influenza, as study staff enrolled one control who tested negative for each positive case in children aged 2 to 8 and 9 to 17. Staff interviewed the patients to collect symptoms, health status, and influenza vaccination history.

Vaccination effectiveness was determined by enrolling 329 children with critical acute respiratory illness -160 were fully vaccinated, 38 were partially vaccinated, and 131 were unvaccinated.

Results from the study determined that vaccine effectiveness against critical illness from any influenza virus was 63%, while a vaccine-match was determined to provide a higher protection rate at 78%. In addition the vaccine was 75% effective against life-threatening illness compared with 57% against non-life-threating illness.

To read more CDC studies click here.