Revised: 1 April 2021

Safety Information

Spontaneous reports: Seasonal influenza vaccination 2020

Influenza vaccines distributed in 2020
Spontaneous reports received in 2020
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Influenza vaccines distributed in 2020

More than 1.7 million doses of influenza vaccine were distributed in 2020, the highest number of doses ever delivered annually. Influenza vaccine distribution also happened earlier and faster than in previous years, due to the COVID-19 pandemic.

See the PHARMAC website for more information about vaccine distribution in 2020.

Spontaneous reports received in 2020

The Centre for Adverse Reactions Monitoring (CARM) received 275 reports of suspected adverse reactions to influenza vaccine in 2020 (Table 1). There were 730 reactions described in the reports. The most commonly reported adverse reactions were injection site inflammation, headache, fever, arm pain and injection site pain (Table 2).

Of the 275 reports, 4.7 percent were considered serious. A serious adverse reaction is defined as any reaction that results in death or is life-threatening, causes or prolongs hospitalisation, results in persistent or significant disability/incapacity, is a congenital abnormality or is a medically important event. Four deaths with a temporal association to the 2020 influenza vaccination were reported to CARM. Causality assessment did not reveal a link to the vaccine for any of the deaths.

In 2020, the majority of reports were submitted by nurses (60.4%), followed by GPs (14.9%) and pharmacists (13.8%). This reporter pattern is similar to previous years.

Table 1: Number of reports of adverse events following influenza vaccination received by the Centre for Adverse Reactions Monitoring and number of influenza doses distributed, 2016–2020

  2016 2017 2018 2019 2020
Number of adverse event reports following influenza vaccination 212 191 232 229 275
Influenza vaccine doses distributeda 1,245,934 1,217,169b 1,317,197 1,505,268b 1,774,269
Estimated reporting rate per 100,000 doses 17.0 15.7 17.6 15.2 15.5


  1. The number of doses distributed is not equal to the number of people who received the vaccine.
  2. The influenza vaccine distribution figures have been updated and differ slightly from those previously published. The estimated reporting rates remain similar.

Table 2: Top five reported suspected adverse reactions for seasonal influenza vaccines, 2020

Adverse reaction Number

Percentage of total reactions

Percentage of total reports

Injection site inflammation 51 7.0 18.5
Headache 32 4.4 11.6
Fever 31 4.3 11.3
Arm pain 29 4.0 10.6
Injection site pain 28 3.8 10.2

More information

Ministry of Health information about influenza

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