Omicron’s new BA.4, BA.5 subvariants: How worried should we be?

Thai health authorities are keeping a close eye on two new Omicron subvariants – BA.4 and BA.5 – that are fast becoming dominant COVID-19strains across the world.

Dr Supakit Sirilak, who leads the Department of Medical Sciences, said BA.4 and BA.5 accounted for 51.7 percent of all COVID-19 infections in Thailand between June 25 and July 1. This percentage is based on an analysis of 948 Omicron cases during that period.

Elsewhere, these subvariants are driving fresh COVID-19 outbreaks in at least 110 nations, raising the number of global infections by 20percent overall. The two subvariants are also being blamed for soaring casualties in three of the six world regions monitored by the World Health Organization (WHO).

Spotlight on new strains

WHO has listed BA.4 and BA.5 as “variants of concern lineages under monitoring” (VOC-LUM). This new category was created earlier this year as a guide to public health authorities across the world about which VOC lineages may need priority attention and monitoring.

According to WHO, VOC-LUM status means that the subvariant shows signs of a transmission advantage compared to other VOC lineages and has additional amino acid changes that are known or suspected to confer observed changes in epidemiology and fitness compared to other variants. These changes mean the two new subvariants are spreading faster than their predecessors.

First detected in January, both BA.4 and BA.5 are sister lineages of Omicron, BA.1 and BA.2. Lab tests in South Africa, where they were first detected, indicate that BA.4 and BA.5 are good at evading protection offered by both previous infections and first-generation COVID-19vaccines.

Though most people in Thailand have received their jabs against COVID-19, these were first-generation vaccines. Next-gen vaccines are not expected to arrive before 2023.

Research suggests that BA.4 and BA.5 are more easily transmissible than their sister subvariant, BA.2, which became the globally dominant strain of COVID-19 earlier this year. The good news is that BA.4 nor BA.5 are not thought to cause more severe symptoms than BA.2.

Research shows that deaths from BA.4/BA.5subvariants are no higher than fatalities caused by other subvariants or earlier variants of COVID-19.

During the first wave of COVID-19 (original variant), the death rate in South Africa was no higher than 5.3 percent. However, the rate soared to 6.9 percent during the Beta-induced wave and hovered at around 6.4 percent during the Delta wave. The first wave of Omicron, caused by the BA.1 subvariant, produced a fatality rate of 2.5percent, which dropped to about 1.9 percent by the time BA.4 and BA.5 arrived. However, this lower fatality rate has also been attributed to the immunity developed from vaccinations and infections.

BA.4 and BA.5 COVID sub-variants may become dominant in Thailand

What will Thailand do?

So far, the Center for COVID-19 Situation Administration (CCSA) has no plans to introduce new measures to combat BA.4/BA.5, given the subvariants are not as severe as the Delta wave that wreaked havoc in Thailand last year.

“But we will continue monitoring these subvariants,” CCSA assistant spokesperson Dr Apisamai Srirangson said.

The Department of Medical Sciences, however, confirmed that some patients in Thailand have died from BA.4 and BA.5.

Hence, health authorities are strongly recommending that people with health conditions that make them vulnerable to COVID-19 get their jabs and booster shots to prevent infection and severe symptoms. Healthy people are advised to continue wearing masks in public places and to wash their hands frequently even though Thailand is now shifting into a post-pandemic mode.

Meanwhile, though booster shots may not prevent breakthrough infections, they do significantly lower the risk of severe illness or death.

According to the US Centers for Disease Control and Prevention, a second booster for people aged 50 and above helps reduce the risk of death by 42times compared to the unvaccinated. A second booster also gives four times more protection than just one booster.

By Thai PBS World’s General Desk


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