CDC: Interim Influenza Vaccine Overall Efficacy Consistent With Previous Flu Seasons

Flu season is in full swing, and activity remains high across 46 jurisdictions across the country according to the CDC’s latest FluView report. There have been 105 influenza-associated pediatric deaths reported during the 2019-2020 season, as of February 15, 2020.¹

Historically, most pediatric deaths occur in children who did not receive the influenza vaccine. Pharmacists can play an important role in administering and educating patients on the importance of annual influenza vaccination.

Study Design and Key Findings

The CDC’s interim report revealed that the influenza vaccine was 45% effective overall against any flu virus.² Additionally, the vaccine offered substantial protection of 55% efficacy against flu among children and adolescents aged 6 months-17 years. These results are consistent with previous flu seasons, ranging from 40% to 60% efficacy.

Data from 4112 children and adults enrolled in the US Influenza Vaccine Effectiveness Network at 5 study sites—1 each in Michigan, Pennsylvania, Texas, Washington, and Wisconsin—during October 23, 2019-January 25, 2020 was used for the study. Patients aged 6 months and older needing outpatient medical care for an acute respiratory illness with cough within 7 days of the onset of symptoms were enrolled in the study once local influenza circulation was identified.²

Study Implications and Influenza Vaccination

The interim report provides important information regarding influenza vaccine efficacy thus far, and it is promising that it currently has substantial protection among children and adolescents. Study limitations include that the end-of-season efficacy estimates could change as additional data become available.² Also vaccination status was self-reported at 4 of 5 sites, which could result in misclassification of immunization status in some patients.²

Annual influenza vaccination is recommended for all patients aged 6 months and older, and it is the best way to protect against the flu.² It is not too late to receive the vaccine, as flu activity remains high across the country. Individuals who are vaccinated and still become infected with the flu generally have less severe symptoms. Additionally, influenza vaccination prevents serious flu-related complications, such as hospitalization and death.

Pharmacists should continue to educate parents on the importance of vaccinating their children. Except for the 2009 pandemic, this flu season currently has the largest number of pediatric deaths since reporting to the CDC began during the 2004-2005 influenza season.²

REFERENCES

• CDC. FluView Weekly U.S. Influenza Surveillance Report. CDC website. https://www.cdc.gov/flu/weekly/index.htm. Last reviewed February 21, 2020. Accessed February 21, 2020.
• Dawood FS, Chung JR, Kim SS, et al. Interim Estimates of 2019—20 Seasonal Influenza Vaccine Effectiveness — United States, February 2020. MMWR Morb Mortal Wkly Rep 2020;69:177—182. doi: http://dx.doi.org/10.15585/mmwr.mm6907a1.