The most recent data demonstrates that the influenza vaccine efficacy was 47% overall and 61% for children between 6 months and 17 years old, according to an interim report published in Morbidity and Mortality Weekly Report by the Centers for Disease Control and Prevention (CDC).
Influenza vaccine effectiveness varies by season. The latest interim report on vaccine effectiveness analyzed data from 3254 adults and children enrolled in the US Influenza Vaccine Effectiveness Network between November 23, 2018 and February 2, 2019. The overall adjusted influenza vaccine effectiveness against influenza infection associated with medically-attended acute respiratory illness was 47% (95% CI, 34%-57%), and the overall effectiveness for children between 6 months and 17 years old was 61% (95% CI, 44%-73%). Of the influenza A viral subtypes, for which information was available, 74% of infections were caused by A (H1N1) pdm09 viruses, against which vaccine effectiveness was estimated to be 46% (95% CI, 30%-58%). The vaccine was least effective for adults aged 50 years and older, for whom the overall effectiveness against all influenza types was 24% (95% CI, -15% to 51%).
The CDC recommended that healthcare providers continue administering the vaccine to patients, as influenza activity is ongoing, and the vaccine is still effective in preventing illness, hospitalization, and death, as well as reduce the severity of influenza-related illnesses. Patients aged 6 months and younger, who have not received the influenza vaccine this season should be vaccinated.
The report’s authors emphasized the importance of vaccinations by stating, “During past seasons, including the 2017-18 season, approximately 80% of reported pediatric influenza-associated deaths have occurred in children who were not vaccinated. Vaccination also has been found to reduce the risk for influenza-associated hospitalization in pregnant women and can reduce the risk for cardiac events among persons with heart disease.” In addition, the study authors concluded, “Influenza activity remains elevated in the United States, highlighting the importance of vaccination.”
Doyle JD, Chung JR, Kim SS, et al. Interim estimates of 2018-19 seasonal influenza vaccine effectiveness — United States, February 2019. Morb Mortal Wkly Rep. 2019; 68(6):135-139.