What To Know About The Current Variants of COVID-19 (SARS-CoV-2)?
Novel variants of COVID-19 (SARS-CoV-2) have been emerging and circulating since the outbreak of the pandemic. This phenomenon is by no means unexpected, uncommon, or exclusive to COVID-19 (SARS-CoV-2). Especially RNA viruses such as coronaviruses and influenza viruses continuously change due to the mutations and recombination that occur frequently during the replication of their genome. Although mutations are a common occurrence for viruses, thankfully, not every alteration of the viral genome results in significant changes in transmissibility, immunity escape, and severity. However, the surveillance of new variants and the assessment of the impact of their mutations on viral characteristics such as transmissibility, disease severity, and immunity escape remain essential.
Several institutions track, classify, and analyze emerging variants through epidemiological studies, laboratory studies, and genetic sequence-based surveillance. Accordingly, institutions such as the World Health Organization (WHO), The Centers for Disease Prevention and Control (CDC), and the UK Health Security Agency (UKHSA) classify emerging variants of COVID-19 (SARS-CoV-2) into differing categories based on characteristics such as transmissibility, symptom severity, and ability to escape immunity. Here’s what the latest reports demonstrate on the current variants of COVID-19 (SARS-CoV-2).
What are Current Variants of Concern (VOC)?
A variant of concern (VOC) is defined as a variant that has been observed as more transmissible, more likely to cause severe symptoms, more likely to evade diagnostic tests, and more likely to escape immunity. Thus, breakthrough infections and reinfections in vaccinated or previously infected individuals are also more common for these variants. So far, the Alpha, Beta, Gamma, Delta, and Omicron variants of COVID-19 (SARS-CoV-2) have been categorized as variants of concern (VOC).
However, these categories change in time and differ in-between regions as variants emerge, circulate, and retreat. WHO currently lists only the Delta (B.1.617.2) and Omicron (B.1.617.2) variants as variants of concern (VOCs). For the Omicron variant, both BA.1, BA.2, BA.3, BA.4, and BA.5 sub-lineages, and recombinant forms such as the XE are included.
Similarly, as of May 5, 2022, the European Centre for Disease Prevention and Control (ECDC) classifies the Delta (B.1.617.2), Omicron BA.1, and Omicron BA.2 as variants of concern. Finally, in the latest technical report by the UK Health Security Agency (UKHSA) dated May 6, 2022, the Omicron BA.1 and BA.2 variants have been listed as variants of concern detected in UK in the past 12 weeks. The report also lists the Beta (B.1.351) variant as a variant of concern identified by the GISAID, although not detected in the UK.
What are Current Variants of Interest (VOI)?
A variant of interest (VOI) refers to variants which have genetic features associated with increased transmissibility, immunity escape, evasion of diagnostic testing, or symptom severity. Although the genomic features of the variant, and in vitro, or epidemiological evidence may suggest significant changes in viral behavior and characteristics, the data is preliminary.
Currently, WHO does not list any variant as variant of interest (VOI). However, in the latest report, the European Centre for Disease Prevention and Control (ECDC) categorizes Omicron subvariants BA.4 and BA.5 as variants of interests (VOI), and the UK Health Security Agency (UKHSA) lists Omicron sub-lineages BA.3 and BA.2.12.1, the recombinant lineage XF, all recombinant lineages of Delta and Omicron variants, along with a BA.1/BA.2 recombinant with the mutation C3583T as variants of interest (VOI).
What are Variants Under Monitoring (VUM)?
Although they might not be a matter of immediate concern, many other lineages are detected and some of them are being monitored due to indications that they might possess properties similar to that of variants of concern (VOI). As epidemiological and in-vitro data extends, these variants may also be categorized under variants of concern (VOC) and variants of interest (VOI). WHO currently lists B.1.640 and XD variants as variants under monitoring, while the European Centre for Disease Prevention and Control (ECDC) categorizes Omicron BA.3 and BA.2 with the mutation L452X.
Will new COVID-19 (SARS-CoV-2) variants continue to emerge?
As mentioned above, especially for an RNA virus such as COVID-19 (SARS-CoV-2), emergence of new variants and subvariants through mutation and recombination is a common occurrence. More variants and subvariants are expected to emerge in the future. Experts also agree that mutations and recombination are more prevalent in environments with high number of infected cases and in which different variants circulate simultaneously. Some experts also warn that COVID-19 (SARS-CoV-2) might form recombinant viruses with different viruses in the future.
Will the COVID-19 vaccines, boosters, and diagnostic tests work on the new variants?
A variant of high consequence (VOHC) refers to a variant which demonstrated clear evidence of evading prevention measures such as diagnostic tests, vaccines, and treatments. A variant of high consequence (VOHC) may reduce the effectiveness of vaccines, leading to disproportionately high numbers of infections in fully vaccinated individuals or lower protection against the development of severe symptoms. Such variants are also likely to reduce the impact of current treatments, which, together with reduced vaccine-induced protection, may result in higher risk of severe disease, along with higher rates of hospitalization and death.
Will the detection of COVID-19 (SARS-CoV-2) be Affected by Variants?
When the variant concept comes true, the detection of COVID-19 (SARS-CoV-2) can be questionable. In the real-time polymerase chain reaction (RT-PCR) tests aspect, if the mutations and mutation types carried by the new variant are known, a new variant detection RT-PCR kit can be obtained by following a comprehensive clinical research. On the other hand, rapid diagnostic tests (RDTs) can be divided by two in accordance with their target regions as antibody and antigen tests. Rapid antigen tests (RATs) use spike proteins and nucleocapsid proteins as targets. In accordance with the mutations’ region of the SARS-CoV-2 virus, sensitivity of a rapid antigen test can reduce for the detection of SARS-CoV-2 (COVID-19) by its target protein. The BA.4 and BA.5 case can be taken as an example: The spike protein region contains the majority of the mutations in the Omicron BA.4 and BA.5 variants. For rapid antigen tests using SARS-CoV-2 spike protein as a target, this can reduce sensitivity or result in non-functional tests. In terms of sensitivity and functionality, those that use nucleocapsid protein as a target, such as our RapidFor™ SARS-CoV-2 Rapid Antigen Test Kit, are less likely to be influenced by mutations.
Likewise, diagnostic tests may fail to detect infections with a variant of high consequence (VOHC) due to significant alterations in targeted proteins. As of now, there has not been any COVID-19 (SARS-CoV-2) variant classified as a variant of high consequence (VOHC). While there is some evidence suggesting that immune responses induced by our current vaccines may be less potent against some of these variants. Booster shots, however, have proved to both strengthen and prolong the protection induced by initial vaccination. Moreover, many experts agree that even if future variants and sub-variants prove to evade the protection offered by our current vaccines, new vaccines can be developed in accordance with the mutations of these variants. Current diagnostic devices can also be improved to according to the unique genomic properties of emerging variants. Altogether, vaccination still remains our most effective measure against the development of severe disease. Vaccination is also the key to reduce viral transmission, contributing to the prevention of the emergence of new variants.