On the heels of a brutal 2017-2018 flu season, the vaccine strains for the 2018-2019 season have been set. The CDC recommends “routine annual influenza vaccination is for all people six months and older if they have no contraindications. Inactivated influenza vaccines (IIVs), recombinant influenza vaccine (RIV), and live attenuated influenza vaccine (LAIV) are expected to be available for the 2018–19 season.”1
Also, recommendations regarding the use of LAIV4 have been revised, putting the mist vaccine popular with children back on the table under certain restrictions.
Citing lack of efficacy, the CDC did not recommend the live vaccine last year or the prior season. The decision to recommend the vaccine came after the CDC’s Advisory Committee on Immunization Practices (ACIP) reviewed several sources of efficacy data.
While including the live attenuated vaccine as an option, ACIP said LAIV4 should not be administered “to children aged 2 through 4 years who have received a diagnosis of asthma or whose parents or caregivers report that a healthcare provider has told them during the preceding 12 months that their child had wheezing or asthma or whose medical record indicates a wheezing episode has occurred during the preceding 12 months.”
In addition, the live vaccine is contraindicated for those who are immunocompromised for any reason. “Close contacts and caregivers of severely immunosuppressed persons who require a protected environment” should not use LAIV4, either. Nor should pregnant women or people who have received antiviral medications within the prior 48 hours, the CDC recommends.
Vaccine Strains
The CDC and its ACIP committee advisors determined the 2018–2019 U.S. trivalent influenza vaccines will include these strains:
- A/Michigan/45/2015 (H1N1)pdm09–like virus
- A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus
- B/Colorado/06/2017–like virus (Victoria lineage).1
“Quadrivalent influenza vaccines will contain these three viruses and an additional influenza B vaccine virus, a B/Phuket/3073/2013–like virus (Yamagata lineage),” the CDC stated.
The overall vaccine efficacy was estimated to be only 40% in the 2017-2018 season.
The main problem was a mismatch between the circulating influenza A (H3N2) strain and the one in the vaccine. For H3N2, the vaccine was only 25% effective, but even that low efficacy reduces the chance of a person seeking medical treatment by one-fourth.
“The 2017-2018 influenza season was a high severity season with high levels of outpatient clinic and emergency department visits for influenza-like illness (ILI), high influenza-related rates, and elevated and geographically widespread influenza activity for an extended period,” the CDC reported.2
Last season, flu illness ran high for a long time — from January 2018 through the end of March.
“ILI peaked at 7.5%, the highest percentage since the 2009 flu pandemic, which peaked at 7.7%,” the CDC concluded.
“ILI was at or above the national baseline for 19 weeks, making the 2017-2018 season one of the longest in recent years.”2
A record number of child deaths occurred in 2017-2018, totaling 180 children. Only 20% of them had been immunized, the CDC reported.
REFERENCES
- Grohskopf LA, Sokolow LZ, Broder KR, et al. CDC. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices—United States, 2018–19 Influenza Season. MMWR 2018;67(3):1–20.
- CDC. Summary of the 2017-2018 Influenza Season. Aug. 31, 2018: https://bit.ly/2rkXwPk.
