Influenza Vaccine

Types of Influenza Vaccine

There are two types of influenza vaccines: an injectible shot and a nasal spray vaccine. Each season three strains of virus are included in the influenza vaccine; two type A viruses and one B virus. For the quadrivalent vaccine, an additional B virus virus is included.

For more information, visit the following links:

Inactivated influenza vaccine or IIV

The inactivated influenza shot contains killed virus. Influenza shots are approved for use in people 6 months and older, including healthy people and people with chronic medical conditions. There are different types of the influenza shots available, including a high-dose vaccine for people 65 years of age and older. The high-dose vaccine is not recommended for people who have had a severe reaction to the influenza vaccine in the past.

Live attenuated influenza vaccine or LAIV

The nasal spray vaccine or LAIV contains the same three virus strains but are weakened live viruses. LAIV is approved for use in healthy people 2-49 years of age who are not pregnant.

Cell-based influenza vaccine

‘Cell-based’ refers to how the influenza vaccine is made. Cell-based influenza vaccines are made by growing viruses in animal cells, rather than in fertilized chicken eggs. The current cell-based influenza vaccine, Flucelvex, is licensed for use in individuals 18 years of age and older.

Jet injector influenza vaccine

Quadrivalent influenza vaccine

The nasal spray vaccine or LAIV contains the same three virus strains but are weakened live viruses. LAIV is approved for use in healthy people 2-49 years of age who are not pregnant.

Egg-based influenza vaccine

Recombinant influenza vaccine

Approved for use in the U.S. market since 2013. Currenlty, recombinant flu vaccine is the only 100% egg-free vaccine on the U.S. market. The produciton of this vaccine does not require the use of eggs. Instead, a specific gene is isolated and combined with portions of another virus that grows well in insect cells.

Influenza Vaccine Virus Strains

There are many different flu viruses, and they are constantly changing. The composition of US flu vaccines is reviewed annually and updated as needed to match circulating flu viruses. This season, all flu vaccines will be designed to protect against the four viruses that research indicates will be most common. Each year, the Food and Drug Administration’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) makes the recommendation for the flu vaccine composition for US flu vaccines.

For 2021-2022, recommendations were made for egg-based, cell-based, and recombinant flu vaccines as listed below:

Egg-based vaccine composition recommendations:

an A/Victoria/2570/2019 (H1N1) pdm09-like virus;
an A/Cambodia/e0826360/2020 (H3N2)-like virus;
a B/Washington/02/2019- like virus (B/Victoria lineage);
a B/Phuket/3073/2013-like virus (B/Yamagata lineage)

Cell- or recombinant-based vaccine composition recommendations:

an A/Wisconsin/588/2019 (H1N1) pdm09-like virus;
an A/Cambodia/e0826360/2020 (H3N2)-like virus;
a B/Washington/02/2019- like virus (B/Victoria lineage);
a B/Phuket/3073/2013-like virus (B/Yamagata lineage).

These recommendations include two updates compared with 2020-2021 US flu vaccines. Both the influenza A(H1N1) and the influenza A(H3N2) vaccine virus components were updated. Compared with the Southern Hemisphere flu vaccine recommendation, this recommendation represents one update and that is to the influenza A(H3N2) component.

Influenza Vaccine Recommendations

To read the 2020-2021 influenza vaccine recommendations, visit the Centers for Disease Control and Prevention (CDC).

Who Should Be Vaccinated

See below for influenza vaccination recommendations for the 2021-2022 influenza season:

Children:

All children aged 6 months–18 years should be vaccinated annually.
Children and adolescents at higher risk for influenza complications, including those who:

are aged 6 months–4 years (59 months)
have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, cognitive, neurologic/neuromuscular, hematological or metabolic disorders (including diabetes mellitus)
are immunosuppressed (including immunosuppression caused by medications or by human immunodeficiency virus)
are receiving long-term aspirin therapy and therefore might be at risk for experiencing Reye syndrome after influenza virus infection
are residents of long-term care facilities; and
will be pregnant during the influenza season.

Note: Children less than 6 months of age cannot receive influenza vaccination. Household and other close contacts (e.g., daycare providers) of children less than 6 months of age, including older children and adolescents, should be vaccinated.

Adults:

Annual vaccination against influenza is recommended for any adult who wants to reduce the risk of becoming ill with influenza or of transmitting it to others. Vaccination is recommended for all adults in the following groups:

persons 19 years of age and older
women who will be pregnant during the influenza season
persons who have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, cognitive, neurologic/neuromuscular, hematological or metabolic disorders (including diabetes mellitus)
persons who have immunosuppression (including immunosuppression caused by medications or by human immunodeficiency virus
residents of nursing homes and other long-term care facilities
healthcare personnel
household contacts and caregivers of children less than 5 years of age and adults 50 years of age and older, with particular emphasis on vaccinating contacts of children less than 6 months of age;
and household contacts and caregivers of persons with medical conditions that put them at higher risk for severe complications from influenza.

Who Should Not Be Vaccinated

Talk with your health care provider before getting the injectable influenza vaccine (shot) or IIV if you:

Have ever had a severe allergic reaction to eggs or to a previous influenza shot or
Have a history of Guillain-Barré syndrome within six weeks following a previous dose of IIV.

If you are sick with a moderate to severe fever when you go to get your influenza vaccine, talk to your doctor or nurse about getting your vaccine at a later date. However, you can get an influenza vaccine at the same time you have a respiratory illness without fever or if you have another mild illness.