10 Influenza

10.7 Expected responses and adverse events following immunisation (AEFI)

Influenza vaccine is well tolerated. Placebo-controlled trials have shown that influenza vaccine may cause systemic reactions (eg, fever, malaise, myalgia) in only 1 percent of adults.51–53 Systemic reactions are more likely in children not previously exposed to the vaccine or virus, starting 6 to 12 hours after immunisation and persisting for one to two days.54

In early 2010 there were reports of children in both Australia and New Zealand who had received the seasonal influenza vaccine and experienced febrile seizures. All of the cases were linked to the Fluvax brand of vaccine.

Vaccinators need to emphasise to recipients that:

Local reactions, including redness and induration at the injection site, may persist for one to two days in 10–64 percent of recipients, but these effects are usually mild. Analysis by gender of 14 studies has revealed that females (both young and elderly) report significantly more local reactions.55 There were no gender differences in seroconversion.

In 2010 an association, probably related to the adjuvant, between one H1N1 pandemic vaccine (not used in New Zealand) and narcolepsy was found. There is now data from a number of countries, which together supports a temporal link.56, 57 However, it is possible that the onset of narcolepsy may be confounded by other factors (such as genetic predisposition, H1N1 influenza and/or other environmental factors).56, 58, 59 Further data is required to confirm the strength of this association and the size of the risk, and to identify the underlying biological mechanisms.60

See section 10.6.2 for information on egg allergy.