Coronavirus variants

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It is typical for viruses to constantly mutate. This is also the case for the SARS-CoV-2 coronavirus.

During the summer of 2023, approximately 90 percent of the SARS-CoV-2 viruses sequenced in Finland are of the XBB recombinant family, with BA.2 and BA.5 sublineages continuing to circulate at a low prevalence. The findings of Finland's SARS-CoV-2 genomic surveillance correspond to variant trends observed elsewhere in Europe.

As viruses proliferate, mutations occur in their genome. Mutations are part of the natural evolutionary process for viruses, and they often take place in the structures of the virus particle that are in contact with the host cell environment. Each virus lineage develops separate lineages at a rate that depends on evolutionary pressure and the characteristics of the virus, and these then evolve into sublineages. During the SARS-CoV-2 pandemic, these mutations have also been commonly referred to as variants.

Several viruses, including the coronavirus, can mutate through a process called recombination. When two viruses infect the same cell at the same time they can exchange genetic material.

Numerous different variants of the coronavirus have circulated around the world, and new ones are constantly developing. Sooner or later, the dominant variants will disappear, either by themselves or through the rise of completely new virus variant.

Monitoring coronavirus variants

Coronavirus lineages are determined from a PCR positive sample, from which the virus is sequenced, i.e. the amino acid sequence of its genome is determined. Sequence data can be used to determine the genetic lineage of a virus and to detect the mutations present within it.

A sample of all COVID-19 cases identified in Finland is selected for sequencing each week in order to assess the situation in different parts of Finland. Wastewater studies of SARS-CoV-2 viruses are also carried out.

Both subvariants and single mutations of the coronavirus are monitored and studied nationally and internationally in order to determine, such things as, possible changes in transmissibility and disease severity as well as vaccine efficacy, drug sensitivity and the effectiveness of diagnostic tests.

The Finnish Institute for Health and Welfare is assessing the spread of variants in cooperation with regional hospital districts, foreign health authorities, the European Centre for Disease Prevention and Control (ECDC) and the WHO.

Naming coronavirus variants

Coronavirus variants have several names that are used in different contexts. The scientific name of a variant stems from its evolutionary lineage.

WHO uses the Greek alphabet to name the most significant variants. Two-letter combinations are used for to mark sublineages. The recombinant coronavirus lineages are named using combinations of letters beginning with X.

Classification of virus variants

Large-scale global sequencing of coronaviruses enables monitoring of the evolution and spread of circulating SARS-CoV-2 lineages. Data of individual lineages is constantly gathered and analysed for assessment of their impact on the SARS-CoV-2 pandemic. WHO designates viral variants with properties that significantly affects the pandemic as variant of concern (VOC), variant of interest (VOI) or variant under monitoring (VUM) -lineages, depending on the degree of evidence. Currently, almost exclusively omicron-descended sublineages are circulating in the world, about ten of which are classified as VOI or VUM lineages. ECDC categorizes variants based on situational assessments of the EU/EEA region and in accordance with the WHO variant definitions.

Omicron

The Omicron variant (B.1.1.529 line) spread widely across the world at the end of 2021, when the BA.1 and BA.2 sublineages caused the fourth wave of coronavirus infections. BA.4 and BA.5 spread around the world in late spring 2022, causing the fifth wave of COVID-19. BA.4 and BA.5 differ from the BA.2 subvariants in four spike protein mutations, and these seem to give them an advantage over the BA.2 subvariant in terms of transmission and bypassing of immune response.

The Omicron variant differs significantly from other coronavirus variants, as 26–32 mutations have been detected in its spike protein. Current research has led to the view that the Omicron variants are more transmissible, cause less serious infections requiring hospitalisation, and bypass immunity from vaccines and prior infections more effectively than the previously dominant variants.

The greater transmissibility of Omicron can be seen especially as an increase in cases of infection within families and as large clusters of infections. Cases are also detected more frequently than before among those who have already recovered from COVID-19 disease and among those who have been vaccinated multiple times. The milder form of the disease can partly be explained by the higher immunity rates from vaccines and infections in the population compared with the time when the Delta variant was the dominant one.

XJ-recombinant

In January 2022, a version of the coronavirus was found in the Västerbotten area originating from the combination of the BA.1 and BA.2 variants. The XJ-recombinant is not believed to significantly deviate from the parent strains. THL stepped up its monitoring of the spread of the XJ recombinant and studied its genetic characteristics and its ability to overcome vaccine protection in collaboration with the University of Helsinki and the Västerbotten healthcare district. The last observations of the XJ recombinant are from summer 2022.
THL and University of Helsinki have found a variant arisen through recombination between Omicron sublineages (3.3.2022)

Vaccines and previous disease provide protection against virus variants

According to current information, the coronavirus vaccines that are now in use offer protection against serious forms of coronavirus disease regardless of what variant of the virus caused the disease. The protective effect against infections is nevertheless weaker against Omicron than against previous variants of the virus. According to current information, prior infection with the disease also protects against serious cases of COVID-19.
Further information: Efficacy of vaccines against COVID-19

How can I protect myself against the coronavirus variants?

The spread of coronavirus variants can be prevented using the same methods that are used against other respiratory tract infections. Vaccinations in accordance with issued recommendations are an important part of protection against all Omicron sublineages.

Prevention of respiratory tract infections

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