Safety of influenza vaccines

Common responses to vaccination

Influenza vaccine is generally well tolerated.

Common responses associated with inactivated influenza vaccines in adults and children include pain and/or redness at the site of injection. Local responses are almost always mild. Systemic events such as headache and fatigue may occur in
adults. Fever, irritability and loss of appetite are more likely to occur in children. These are generally mild and of short duration. Other systemic events such as muscle aches or cough may appear influenza-like. However, the influenza vaccine
currently used in New Zealand does not contain live viruses and cannot cause the disease.

Serious events associated with influenza vaccine

The most significant serious reaction associated with influenza vaccination is anaphylaxis, a serious allergic reaction that usually comes on within minutes of receiving the vaccine. This occurs around once in a million influenza vaccine doses. 

With the possible exception of Guillain-Barré syndrome, other serious adverse events, such as onset of autoimmune conditions, are no more likely to occur in vaccinated persons compared with unvaccinated people.

Guillain-Barre Syndrome and influenza vaccine

Guillain-Barré syndrome (GBS) has an annual incidence of around 1–4 cases per 100,000 people worldwide.

During a swine influenza vaccination campaign in the United States in the 1970s, an increase in GBS was observed in vaccine recipients (around one case per 100,000 vaccinations) and the vaccination campaign was halted and surveillance of GBS expanded.

Epidemiological studies since then have suggested either no increased risk or a possible slight increase in risk of around one case per million adult influenza vaccinations. A recent meta-analysis of these studies identified a small increase in the risk of GBS following influenza vaccination. However, studies have also identified that the risk of GBS following an episode of influenza-like illness is significantly higher than the risk following influenza vaccination, especially in older adults. This highlights the importance of balancing the potential risks of disease with the potential risks and benefits of influenza vaccination to make an informed decision.

Febrile adverse events

Fever is a common adverse event in children after vaccination. Convulsions associated with fever can occur in susceptible children. Around 3–8 children in 100 aged less than 7 years will experience a febrile convulsion, most likely when aged between 16 and 30 months.

Studies identified an increased risk of fever 38°C or over in children aged 6–23 months when an influenza and 13-valent pneumococcal conjugate vaccine PCV13 (PREVENAR 13®) vaccines were administered concurrently. Parents/guardians whose children are recommended to receive both influenza vaccine and PCV13 should be advised of the increased risk of fever following concurrent administration of these vaccines. Separating administration of these vaccines by two days can be offered, but is not essential.

For the PREVENAR 13® Datasheet please refer to the Medsafe website

Reporting adverse events following influenza immunisation

Health professionals/vaccinators are professionally and ethically responsible for reporting any serious or unexpected adverse events after the administration of all medicines including the influenza vaccine regardless of whether or not they consider the event to have been caused by the vaccination.
Information should include:

  • individual’s details
  • the vaccine administered
  • vaccine batch number
  • date of onset of symptoms
  • type and duration of adverse event
  • treatment required
  • outcome if known but do not delay reporting whilst waiting outcome information

Some providers are able to report events through their practice management system. Reports can be completed online or the form can be downloaded and printed using the above link, completed and mailed to:

Freepost 112002
The Medical Assessor
Centre for Adverse Reactions Monitoring (CARM)
PO Box 913, Dunedin, 9710
or faxed to: (03) 479 7150