DNA Explainer: Delta, Mu, C.1.2 - Why new COVID-19 variants have raised fears of vaccine resistance

Even as the world is facing the repercussions of the deadly Delta variant of COVID-19, the main cause behind the second wave outbreak in India, two other strains of the virus has become a cause of concern globally.

C.1.2 COVID-19 variant, first detected in South Africa in May, and Mu also known by its scientific name as B.1.621, first identified in Colombia in January, have been said to be a major cause of concern for the scientists.

The World Health Organisation said that it is closely monitoring the new 'variant of interest' Mu or B.1.621 warning that it could be more vaccine-resistant. Mu has been behind the outbreaks in South America and Europe.

New cases of the Mu variant have also been reported in the UK, Europe, the US, and Hong Kong. The new 'variant of interest' Mu is being closely monitored, the UN health agency said.

On the other hand, the C.1.2 lineage of COVID-19 is creating havoc in South Africa. WHO has not yet declared this strain of COVID-19 as a variant to follow or a 'variant of concern' till now.

Today, we try to critically examine why experts fear the new lineage of COVID-19 variants like Delta, Mu, C.1.2 which are considered more dangerous than the original Wuhan virus.

WHO says that the primary reason behind this fear is that these three new strains of the COVID-19 virus have a number of mutations that suggest it could be more resistant to vaccines

Mu or B.1.621 variant

The Mu variant has a number of mutations that suggest it could be more resistant to vaccines, the WHO warned.

The new variant detected in 39 countries was found to possess a 'constellation of mutations that indicate potential properties of immune escape'. Mu is the fifth 'variant of interest' to be monitored by the World Health Organisation (WHO) since March this year.

The global prevalence of the Mu variant among sequenced COVID-19 cases is currently below 0.1%. But it has consistently increased in countries like Colombia with 39% and Ecuador with a 13% increase.

The preliminary data shows it may evade immune defences in a similar way to the Beta variant first discovered in South Africa. However, more studies are required to understand the phenotypic and clinical characteristics of this variant, the UN health agency said.

C.1.2 variant of COVID-19

This has mutated substantially compared to C.1, which dominated the COVID-19 first wave in South Africa. Scientists are of the opinion that the strain may have a greater ability to evade antibodies that protect the body from the COVID-19 virus. 

C.1.2 may have more immune evasion properties than the Delta variant based on its pattern of mutations, says Richard Lessells, infectious disease specialist. The study says the C.1.2 lineage has a rate of about 41.8 mutations per year, twice as fast as the current global mutation rate.

It is not a single virus but a clustering of genetically similar viruses known as C.1.2. Researchers found that the cluster picked up a lot of mutations in a short period of time. 

Delta variant

The Delta variant may be one of the reasons behind a reduced vaccine efficacy among US healthcare workers. Researchers from the University of California San Diego Health pointed out that a large number of healthcare workers became COVID positive.

As per UCSDH, despite 83% of healthcare workers being vaccinated, many of them got infected with COVID-19 in July. Vaccination in the United States with mRNA COVID-19 vaccines began in mid-December 2020.

According to the researchers, infections had decreased dramatically by early February 2021. However, the Delta variant accounted for over 95% of UCSDH cases by the end of July, the researchers said.