Seasonal Influenza Vaccination

The Australian Technical Advisory Group on Immunisation (ATAGI) has published advice on the use of seasonal influenza vaccines for 2022.

Some of the key points include:

• Annual vaccination is recommended for all people six months of age and older to prevent influenza and its complications;
• Influenza vaccines can be administered on the same day as any COVID-19 vaccine;
• A 2022 influenza vaccine is recommended even if a 2021 influenza vaccine was administered in late 2021 or early 2022; and
• Adults 65 years of age and older are recommended to receive Fluad® Quad or Fluzone® High Dose Quadrivalent.

Vaccine choice:

Eight influenza vaccines are available in Australia this year, all of which are quadrivalent. The choice of vaccine type is primarily influenced by the patient’s age and availability on the National Immunisation Program (NIP).

Cell-based

Flucelvax® is the only cell-based influenza vaccine available. It is produced using mammalian cell culture instead of hens’ eggs. This cell-based production method may produce a closer vaccine match by avoiding egg-adapted mutations. This may improve vaccine effectiveness, although some clinical studies demonstrate that these differences may be small. Flucelvax® is available on the private market; it is not funded on the NIP.

Egg-based

The other influenza vaccines are cultivated in embryonated hens’ eggs. Whilst these vaccines may contain traces of ovalbumin (<1mcg per vaccine dose), they are considered safe for egg-allergic individuals. The Australasian Society of Clinical Immunology and Allergy (ASCIA) provides detailed information on vaccination in individuals with egg allergy. They recommend that egg-based influenza vaccines may be administered as a single dose followed by the usual 15-minute observation period. Split dosing and allergy testing prior to vaccination are not recommended. This advice is supported by a recent review of 28 studies, including over 4,000 individuals with egg allergy, 656 of whom had a history of egg anaphylaxis. No severe reactions were reported after influenza vaccination in this review.

Older adults

There are two brands specifically indicated for use in older adults:

1. Fluzone® High-Dose is indicated for use in adults 60 years of age and older. This vaccine contains 60mcg of influenza virus haemagglutinin for each of the four strains. In comparison, standard-dose vaccines contain 15mcg of haemagglutinin for each strain. Fluzone® High-Dose is not funded on the NIP.
2. Fluad® Quad is available on the NIP for adults 65 years of age and older. This formulation contains the standard 15mcg of haemagglutinin for each strain, but also contains an adjuvant to increase its immunogenicity.

ATAGI advises that adjuvanted influenza vaccines may provide greater protection against influenza disease-related outcomes, particularly critical outcomes such as hospitalisation. However, the incidence of non-serious local adverse events is slightly higher for adjuvanted influenza vaccines.

Children

There are four brands available for children from six months of age:

• Fluquadri®;
• Fluarix® Tetra;
• Influvac® Tetra; and
• Vaxigrip® Tetra.

Flucelvax® Quad may be used in children from two years of age and Afluria® Quad is for children from five years of age.

Funded vaccines:

Influenza vaccines are available for free on the National Immunisation Program (NIP) for all children aged six months to five years and all adults aged 65 years and older. Other specific populations with an increased risk of influenza complications (e.g. pregnant women, Aboriginal and Torres Strait Islander people, and people with certain medical conditions) may also receive influenza vaccination under the NIP.

The medical conditions that confer eligibility for funded vaccination are those associated with an increased risk of influenza disease complications, including:

• Certain cardiac diseases (e.g. congestive heart failure);
• Certain chronic respiratory conditions (e.g. severe asthma, cystic fibrosis, chronic obstructive pulmonary disease);
• Certain chronic neurological conditions (e.g. seizure disorders, neuromuscular disorders);
• Immunocompromising conditions (e.g. immunocompromise due to disease or treatment, asplenia, splenic dysfunction, HIV infection);
• Diabetes (type 1 or 2)
• Chronic metabolic disorders;
• Chronic renal failure;
• Haemoglobinopathies;
• Children aged 5-10 years who are taking long-term aspirin therapy (due to an increased risk of Reye syndrome following influenza infection).

Full details on NIP eligibility can be obtained from the Department of Health.

The Australian Immunisation Handbook also strongly recommends influenza vaccines for additional populations that would not be eligible under the NIP. This includes:

• People with
  • Chronic liver disease
  • Down syndrome
  • Obesity (BMI ≥ 30kg/m²)
  • Harmful use of alcohol
• Occupational groups
  • Healthcare workers
  • Staff and residents of aged care and long-term residential facilities
  • Essential services providers
• People who are travelling during influenza season.

Interactions:

ATAGI advise that influenza vaccines may be administered on the same day as COVID-19 vaccines. The safety of administering multiple adjuvanted vaccines on the same day has not been studied. Therefore, it would be preferable for patients receiving the adjuvanted Fluad® Quad to separate the administration of Shingrix® by a few days. However, ATAGI advises that co-administration of these two vaccines is acceptable if necessary.

Summary

A summary of approved influenza vaccines is shown in Table 1. The individual product information should be reviewed for further details.

Table 1. Overview of 2022 influenza vaccines

*Primarily available on the private market, but will be available on the NIP as a backup.