Annual vaccination against influenza A and B viruses is recommended for everyone ≥6 months old without a contraindication. The authors provide a list of available vaccines and recommendations for specific patient populations for the 2019-2020 season.

TIMING — In the US, influenza vaccine should be offered by the end of October and continue to be offered for as long as influenza is circulating in the community. Early vaccination may result in suboptimal immunity before the end of the influenza season. Children who require 2 doses should receive the first dose as early as possible.

COMPOSITION — All seasonal influenza vaccines available in the US contain antigens of the same two influenza A viruses. Trivalent vaccines contain only one influenza B virus antigen. Quadrivalent vaccines contain influenza B virus antigens from both genetic lineages that have been circulating globally since the 1980s. Children are more likely than adults to become infected with influenza B.

EFFECTIVENESS — Influenza vaccination reduces the incidence of laboratory-confirmed influenza and can reduce the risk of serious complications and death associated with influenza illness. The effectiveness of the influenza vaccine during the 2018-2019 season was 47% (61% in children 6 months-17 years old and 24% in adults ≥50 years old).

LIVE-ATTENUATED VACCINE — FluMist Quadrivalent, the intranasally administered live-attenuated influenza vaccine, is FDA-approved for use in healthy nonpregnant persons 2-49 years old, and it is recommended by the Advisory Committee on Immunization Practices (ACIP) and the American Academy of Pediatrics (AAP) recommend as an option this season.

OLDER ADULTS — Older adults may have weaker immunogenic responses to influenza vaccination than younger adults, and their antibody levels may decline more rapidly. The following vaccines can improve antibody responses in these patients: 1) recombinant vaccine (Flublok Quadrivalent, a recombinant inactivated vaccine, contains three times the amount of antigen included in standard dose influenza vaccines and is FDA-approved for persons ≥18 years old); 2) high-dose vaccine (Fluzone High-Dose, an inactivated trivalent vaccine, contains four times the amount of antigen included in standard-dose influenza vaccines, and it is FDA-approved for persons ≥65 years old); 3) adjuvanted vaccines (Fluad, an adjuvanted inactivated trivalent influenza vaccine which contains MF59, is FDA-approved for use in persons ≥65 years old).

PREGNANCY — Vaccination protects pregnant women against influenza-associated illness, and their infants for up to the first 6 months of life. The ACIP and the American College of Obstetricians and Gynecologists recommend vaccinating pregnant women against influenza without regard to the trimester of pregnancy, but they should not receive the live-attenuated vaccine.

ALLERGY — The ACIP, the American Academy of Allergy, Asthma and Immunology, and the American College of Allergy, Asthma and Immunology state that any age appropriate influenza vaccine can be administered to persons who report a history of hives related to egg exposure. Persons with more severe egg allergy should be vaccinated in a healthcare setting. The recombinant vaccine (Flublok Quadrivalent) and the cell culture-based inactivated vaccine (Flucelvax Quadrivalent) are not prepared by propagation of virus in embryonated eggs.

IMMUNOCOMPROMISED PERSONS — The live attenuated influenza vaccine should not be used in these subjects; inactivated vaccines are generally safe, but the immune response may be reduced.

ADVERSE EFFECTS — Influenza vaccination has been associated with a very low absolute risk of Guillain-Barré syndrome. Except for soreness at the injection site, adverse reactions to inactivated influenza vaccines are uncommon. The most common adverse reactions associated with the live-attenuated vaccine are runny nose, nasal congestion, fever, and sore throat.

WITH OTHER VACCINES — Inactivated and recombinant influenza vaccines can be administered concomitantly or sequentially with live or other inactivated vaccines. The live-attenuated influenza vaccine can be given simultaneously with inactivated or other live vaccines. Other live vaccines not administered on the same day should be given at least 4 weeks later.

WITH INFLUENZA ANTIVIRALS — Use of influenza antiviral drugs within 48 hours before or <2 weeks after administration of the intranasal live-attenuated influenza vaccine could inhibit replication of the vaccine virus, reducing the vaccine’s efficacy.