2018-2019 Flu Vaccine Recommendations from ACIP

New recommendations from the US Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) reveal that health care providers have the intranasally-administered live attenuated influenza vaccine (LAIV) among their arsenal of available vaccines for the 2018-2019 flu season.

The reintroduction of intranasal LAIV vaccine is based on data on its effectiveness from previous seasons, including data from 5 US observational studies and a systematic review and meta-analysis of US and non-US studies. Although previous LAIV vaccines were found to have poor effectiveness against influenza A(H1N1)pdm09-like viruses, they proved effective against influenza B viruses, which tend to be responsible for the marked uptick in infections during the second half of the flu season. Furthermore, manufacturer data suggest that the new H1N1pdm09-like virus included in the 2018-2019 vaccines “has improved replicative fitness over previous H1N1pdm09-like viruses included in LAIV,” according to CDC’s Morbidity and Mortality Weekly Report (MMWR).

The types of available vaccines for the 2018-2019 flu season include the LAIV and recombinant influenza vaccine (RIV) as quadrivalent vaccines, and inactivated influenza vaccines (IIVs) as both a high-dose IIV trivalent and adjuvanted IIV trivalent.

As Contagion® reported in March, the influenza strains to be included in the trivalent vaccines include:

• Influenza A/Michigan/45/2015 (H1N1)pdm09-like virus
• Influenza A/Singapore/INFIMH-16-0019/2016 (H3N2)-like virus Replaces A/Hong Kong/4801/2014 (H3N2)-like virus from the 2017-2018 northern hemisphere influenza vaccine
• Influenza B/Colorado/06/2017-like virus (B/Victoria/2/87 lineage) Replaces B/Brisbane/60/2008-like virus from the 2017-2018 northern hemisphere influenza vaccine

Influenza strains to be included in the quadrivalent vaccines are the same as the trivalent, plus:

• Influenza B/Phuket/3073/2013-like virus (B/Yamagata/16/88 lineage)

The recommendations note that for patients who receive the LAIV4, the effectiveness of the vaccine may be reduced if influenza antiviral medications are taken 48 hours prior, or up to 14 days after, vaccination. Patients vaccinated with the LAIV4 who take antivirals during those time periods may be revaccinated with another appropriate vaccine.

Individuals with a history of egg allergy, regardless of severity, can receive “any licensed, recommended, and age-appropriate influenza vaccine (IIV, RIV4, or LAIV4),” according to the updated recommendations.

Recent labeling changes and licensures include an expansion of the age indication for the Afluria Quadrivalent (IIV4) vaccine to now include patients 5 years or older (from 18 years or older) and for the Fluarix Quadrivalent (IIV4) to include patients 6 months of age or older (previously indicated for patients 3 years of age or older).

Because the duration of the influenza season varies, vaccination efforts should continue throughout the season; however, ACIP recommends that patients should receive the influenza vaccine before the end of October to ensure the vaccine remains effective throughout the flu season. An analysis by the US Influenza Vaccine Effectiveness Network indicated that vaccine effectiveness (VE) “declined by about 7% per month for H3N2 and influenza B, and 6% to 11% per month for H1N1pdm09” for the 2011-2012 through 2014-2015 flu seasons, according to the report. Additionally, VE stayed at greater than 0 “at least 5 to 6 months after vaccination.” Available data indicate that from the 1982-1983 influenza season through the 2017-2018 influenza season, peak influenza occurred in January or later and, “in 58% of seasons, the peak was in February or later.”