New variants of COVID-19

New variants of COVID-19 have emerged in several places around the world. One of these new variants, the Delta variant, is now the main variant everywhere, including in Aotearoa New Zealand.

On this page, you can find the following information:

Is it normal for viruses to change?

It is normal for viruses to constantly change. This is known as mutation. These changes create new strains or variants of viruses. Read about why and how viruses change

Many variants of the virus that causes COVID-19 have been found around the world during this pandemic and have spread to other countries. They are now named using the Greek alphabet according to the order in which they have been identified. Current known variants are Alpha (identified in the UK), Beta (identified in South Africa), Gamma (identified in Brazil) and Delta (identified in India).

The Delta variant is the most transmissible variant, spreading a lot more easily than the original version of the COVID-19 virus and other variants.

What does the Delta variant mean for New Zealanders?

The Delta variant has a number of differences compared to earlier versions of the virus. These differences mean that the Delta variant is a greater threat to the health of people who contract the infection. It is also a greater challenge to contain the spread of the virus in an outbreak. 

  • Delta can cause people to develop more serious COVID-19 illness than other variants of the virus.
  • People with a Delta infection are at higher risk of needing to be in hospital.
  • The chance of infecting others, such as people within your household or other contacts, is very high because Delta is so transmissible.
  • It is estimated that on average, one person infected with Delta may infect 5 or 6 other people. This is how Delta outbreaks have grown so rapidly overseas and in Aotearoa New Zealand.
  • People with Delta infections seem to carry much more virus (have a higher viral load) and for a longer period of time than those infected with the original virus or other variants.
  • The time from exposure to the virus until first symptoms is shorter for the Delta variant.
  • Some people may have no symptoms (asymptomatic) when infectious.  

This means it is so important to stamp out any community outbreaks as quickly as possible and to ensure very high rates of vaccination. It is also even more important that everyone follows the government's advice on what to do to stop the spread.

What to do to stop the spread of the Delta variant

  • Physical distancing of 2m where possible.
  • Wear a face covering or mask on public transport and indoors in busy places such as supermarkets.
  • Keep indoor rooms well ventilated (eg, by opening windows and doors) where possible.
  • Stay home if you're sick. If you show any symptoms, phone your GP or Healthline (0800 358 5453) and get a COVID-19 test.
  • Use the NZ COVID Tracer app and turn on Bluetooth on your phone. 
  • Wash your hands often.
  • Cough or sneeze into your elbow.
  • Clean surfaces regularly.
Read more about stopping the spread.

Does the COVID-19 vaccine work on the COVID-19 Delta variant?

Being fully vaccinated gives you a high degree of protection against Delta infection, and an even higher degree of protection against severe illness, hospitalisation and death. Evidence currently shows the effectiveness of 2 doses of the Pfizer vaccine against illness due to Delta infection is about 88% and the protection against hospitalisation due to Delta infection about 96%.

However, no vaccine is 100% effective so there is some chance that a vaccinated person may become infected with the Delta variant and may transmit the virus to other people. Taking other precautions will remain important in order to continue to protect our communities. Read more about the Pfizer COVID-19 vaccine and the COVID-19 vaccine roll-out


  1. New COVID-19 variants Centers for Disease Control and Prevention, US, 2021
  2. The effects of virus variants on COVID-19 vaccines World Health Organization, 2021
  3. COVID-19 – about the Delta variant Ministry of Health, NZ, 2021

Reviewed by

Dr Jeremy Tuohy is an Obstetrician and Gynaecologist with a special interest in Maternal and Fetal Medicine. Jeremy has been a lecturer at the University of Otago, Clinical leader of Ultrasound and Maternal and Fetal Medicine at Capital and Coast DHB, and has practiced as a private obstetrician. He is currently completing his PhD in Obstetric Medicine at the Liggins Institute, University of Auckland.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Jeremy Tuohy, Capital and Coast DHB and University of Auckland Last reviewed: 23 Apr 2021