Fever following administration of two inactivated influenza vaccines--a survey of parents of New Zealand infants and children 5 years of age and under

Due to a dramatic increase in reported febrile convulsions in Western Australia following a routine pediatric influenza vaccination programme we evaluated parental recall of fever in their child following 2010 trivalent influenza vaccine manufactured by either Sanofi Pasteur (Vaxigrip^®) or CSL Biotherapies (Fluvax^®) to determine if the rates of febrile events in infants and children 5 years and under following administration of either Vaxigrip^® or Fluvax^® were significantly different.

Method

A convenience sample of New Zealand General practices who had received stocks of the vaccines of interest consecutively contacted parents of infants and children under 5 years of age who received at least one dose of 2010 influenza vaccine. A brief questionnaire was administered with the main outcome parental recall of fever within 24 h of vaccination.

Results

Response rate was 99%. There were 327 parents of children aged 6 months to 5 years attending one of 23 primary care practices who had received a dose of either the Vaxigrip^® or Fluvax^® vaccine between 4th March and 28th June 2010 surveyed. A total of 422 doses were given of which 267 were Vaxigrip^®, 133 were Fluvax^® and 22 another vaccine. Fever occurred significantly more frequently within 24 h following administration of Fluvax^® compared with Vaxigrip^® RR 4.33 (2.44-7.70). When fevers were measured they were, on average, higher in the Fluvax^® vaccines (38 °C compared with 39 °C). Additionally, recipients were more likely to seek medical advice for fever following Fluvax^® RR 23.11 (2.96-180.12).

Conclusions

There is considerable variation in reactogenicity between two 2010 seasonal vaccines in infants and young children. Vaxigrip^® is significantly less reactogenic when compared to Fluvax^® in this population in which Fluvax^® is associated with unacceptably high rates of febrile reactions. There has been insufficient safety evaluation of seasonal influenza vaccine safety in this population.