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About SARS-CoV-2 variants
All viruses change over time. This includes SARS-CoV-2, the virus that causes COVID-19.
Most changes have little to no impact on the virus’s properties.
However, some changes may affect:
- how easily the virus spreads
- disease severity
- the ability of vaccines to prevent disease
- the effectiveness of treatments, diagnostic tools and other public health and social measures.
Variants of interest and variants of concern
Many different SARS-CoV-2 variants have emerged over the course of the pandemic.
Variants that have changed the virus’s properties are called variants of interest by the World Health Organization (WHO). These are monitored more closely.
Variants of interest that significantly change the way the virus behaves and present an increased public health risk are called variants of concern.
Main variants of concern
The five main variants of concern during the COVID-19 pandemic have been:
- Alpha (B.1.1.7)
- Beta (B.1.351)
- Gamma (P.1)
- Delta (B.1.617.2)
- Omicron (B.1.1.529).
Monitoring changes to the COVID-19 virus
WHO and its international networks of experts monitor changes to the virus. Significant changes to the virus structure and its properties may be met with an updated public health response.
Tracking SARS-CoV-2 variants – WHO
Detecting variants
Genomic sequencing
Whole-genome sequencing identifies which variant a person is infected with. This is possible for samples collected for PCR testing but not through rapid antigen testing (RAT).
In New Zealand, ESR’s COVID-19 genomics insights dashboard reports trends and insights from whole-genome sequencing surveillance here and overseas.
COVID-19 genomics insights dashboard – ESR
Wastewater surveillance
In New Zealand ongoing wastewater surveillance is carried out by ESR to monitor variants circulating in the community.
COVID-19 wastewater dashboard – ESR
Omicron
Omicron was first identified in mid-November 2021. WHO quickly classified Omicron as a variant of concern due to the large number of mutations it contains.
Omicron is much more transmissible than previous variants of the COVID-19 virus. Like other variants, it continues to evolve. Omicron has spread rapidly worldwide and is now the sole variant in most countries.
Omicron less likely to cause severe illness
People are less likely to be severely ill if they contract Omicron rather than Delta.
Omicron has resulted in many more people being hospitalised than at any other time in the pandemic. This is not because Omicron is very severe but because Omicron is more transmissible. it can cause many infections over a short period of time.
Omicron can still cause severe illness and even death, especially for the elderly and those with severe underlying health conditions. Māori and Pacific populations experience higher age standardised rates of hospitalisation and death due to COVID-19.
Being up to date with COVID-19 vaccinations can help reduce risk of severe illness and/or death due to COVID-19.
However, fewer people infected with Omicron are hospitalised compared to those infected with Delta.
Omicron in New Zealand
Omicron was first detected in New Zealand in an international traveller in managed isolation who arrived in the country on 10 December 2021. Managed isolation was still in use at that time, and community spread of Omicron was not detected until mid-January.
Omicron subvariants
Two Omicron subvariants (BA.1 and BA.2) were detected in New Zealand in January 2021. BA.2 became dominant during the first 3 months of 2022.
Numerous Omicron subvariants have since been detected in New Zealand.
New variants of Omicron continue to emerge, but there does not appear to be a change in the severity of disease due to these variants. That means the public health settings in place to manage current Omicron variants are appropriate for managing subvariants present in our community.
Vaccination and Omicron
The Omicron variant has changes to the spike protein the virus uses to gain access to cells. The spike protein is targeted by many vaccinations, including the original Pfizer vaccine, which was developed to protect against the original SARS-CoV-2 virus.
Pfizer’s bivalent vaccine was developed to provide better protection against Omicron. The vaccine induces the immune system to produce antibodies against spike proteins from both the original variant of SARS-CoV-2 and Omicron subvariants. From 7 March 2024, the Pfizer XBB1.5 monovalent vaccine replaced the bivalent vaccine to provide better targeting of newer Omicron strains.
COVID-19 vaccines – Health New Zealand
Delta
The Delta variant was first detected in late 2020. It was named a variant of concern by WHO on 31 May 2021. Delta is more transmissible than previous variants and spread rapidly worldwide.
WHO now considers Delta a previously circulating variant of concern.
Delta in New Zealand
In August 2021, the Delta variant arrived in New Zealand.
Delta posed very different challenges to earlier strains of COVID-19, with its rapid transmission, infectiousness and higher risk of needing hospital care. People who were not vaccinated were most at risk of severe illness.
Omicron has since replaced Delta as the predominant variant. The Delta variant has not been detected in New Zealand since 2 March 2022.
Delta Response Rapid Review
An independent review into the Ministry’s response to the August 2021 Delta outbreak is available.
COVID-19 Variants of Concern Framework
The Strategic Framework for COVID-19 Variants of Concern was released in June 2022. The framework has since been replaced by the Aotearoa New Zealand Strategic Framework for Managing COVID-19.
