Drug class · Respiratory

Influenza vaccines

Also known as: flu vaccines

Seasonal vaccines against influenza A and B, reformulated every year: inactivated injected vaccines for most people and a live attenuated nasal spray for children.

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Biological target
Influenza virus haemagglutinin (immune response)
Also called
flu vaccines

Mechanism of action

Each formulation presents the immune system with haemagglutinin from the strains expected that season, either as inactivated virus fragments or, in the nasal spray, as weakened live viruses that replicate only in the cooler nose. Antibodies and memory cells form over about two weeks; the antibodies neutralise the virus at the airway surface and the memory cells speed the response if infection occurs. Because circulating strains drift, the strains are reselected annually and immunity from one season fades.

Members of the class

inactivated influenza vaccineadjuvanted inactivated influenza vaccinehigh-dose inactivated influenza vaccinerecombinant influenza vaccinelive attenuated influenza vaccine (nasal)

Members with a page on this site are linked.

Conditions treated

PneumoniaAsthmaChronic obstructive pulmonary disease (COPD)Heart failure

Class effects

  • Sore arm, mild fever and aches for a day or two
  • Nasal congestion after the live nasal spray

Cautions

  • Previous severe allergic reaction to the vaccine
  • The live nasal spray is avoided in significant immunosuppression, pregnancy and severe asthma
  • Postponed during a feverish illness

Class interactions

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Educational content. A drug class page describes what a family of medicines has in common. Individual medicines differ in dose, licensing and interactions; treatment choices belong to a prescriber.