Highly contagious COVID-19 subvariants pose threat to immune protection

pharmafile | July 7, 2022 | News story | Business Services  

The COVID-19 subvariants BA.4 and BA.5 have been found to be the most contagious variants yet, and are better able to evade immunity afforded by vaccines and previous infections. The BA.5 subvariant accounted for nearly 54% of the US’ COVID-19 cases, as of 2 July.

An FDA advisory committee has recommended that COVID-19 vaccine makers target these two subvariants of Omicron. The CDC reported in June that the Omicron subvariants BA.4 and BA.5 had become dominant in the US. This was revised on 5 July, stating that BA.5 infections made up over half on new cases.

“They’re taking over, so clearly they’re more contagious than earlier variants of omicron,” shared David Montefiori, a professor at the Human Vaccine Institute at Duke University Medical Centre. He went on to highlight that BA.4 and BA.5 are an estimated three times less sensitive to the existing neutralising antibodies from current COVID-19 vaccines, compared to the original variant, BA.1.

Further research has suggested that BA.4 and BA.5 are four times more resistant to antibodies from vaccines than BA.2. This more transmissible subvariant of Omicron replaced the original variant as the US’ dominant cause of cases in April 2022, during which time it accounted for around 60% of cases.

Omicron began as three subvariants, BA.1, BA.2, and BA.3. All were genetically distinct enough to be categorised as separate variants. A recent pre-print publication from a series of lab-based, cell-culture experiments by a research group in Japan found that BA.4/5 was able to replicate more effectively in the lungs than in BA.2. In hamster experiments, the subvariant developed into more serious disease. However, data from South Africa and the UK has found that the surge in BA.4/5 cases did not see a major increase in severe disease and death. 

Francois Balloux, director of the University College London Genetics Institute, shared that the resistance of the subvariants to antibodies from vaccines is the likely reason these variants have taken over, NBC reported: “At this stage now, I think all these variants actually are roughly equally transmissible, so there’s not a huge difference,” he said.”It’s just some are slightly better at infecting people who have been vaccinated or infected by previous variants.”

Ana Ovey

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