Covid-19: New Omicron Sublineages BA.4 and BA.5 Likely To Evade Vaccines And Natural Immunity

New omicron sublineages found by South African scientists this month are likely able to resist vaccines and natural immunity from earlier infections, as said by the head of the gene sequencing teams that generated a report on the strains.

According to Tulio de Oliveira, the dean of the institutions at the universities of KwaZulu-Natal and Stellenbosch, the new omicron sublineages BA.4 and BA.5 appear to be more infectious than the previous BA.2 lineage, which was considered to be more infectious than the initial omicron variety.

The current surge in covid-19 cases means that the strains are more likely to be capable of evading the body's defences rather than simply being more transmissible, according to de Oliveira. This is because almost everyone in South Africa has either been vaccinated against the coronavirus or has had a prior infection.

There are "mutations in the lineages that allow the virus to evade immunity," he said in a response to queries. "We expect that it can cause reinfections and it can break through some vaccines, because that's the only way something can grow in South Africa where we estimate that more than 90% of the population has a level of immune protection."

Early warning

South Africa is seen to be a leading indicator of how the omicron variants and their sublineages will affect the population of the world. In November, scientists from South Africa and Botswana discovered omicron, and South Africa was the first country to see a significant increase in infections as a result of the variation.

According to de Oliveira's Twitter posts, the new sublineages account for almost 70% of new coronavirus cases in South Africa.

"Our main scenario for Omicron BA.4 and BA.5 is that it increases infections but that does not translate into large hospitalizations and deaths," he said.

On Thursday, South Africa registered 4,146 new cases, with an 18.3 per cent test positivity rate. On March 28, there were 581 instances with a 4.5 per cent positive rate.

"It is not clear if South Africa has entered the fifth wave, but the numbers suggest that we are on the brink of one," Health Minister Joe Phaahla said on a conference call on Friday. "Experts have told us that the fifth wave was expected to begin towards the middle of May."

The central Gauteng province has reported more than half of the new illnesses, with the coastal KwaZulu-Natal and Western Cape regions accounting for the majority of the remaining cases.

"What is clear is that we are still at great risk of Covid-19, especially as we go into a very long winter where people spend more times indoors, which brings the risk of high spread," Phaahla said. "The Easter and other religious holidays could have resulted in a spike of infections."

On the call, Waasila Jassat, a public health specialist at the National Institute of Communicable Diseases, indicated that while hospitalizations are increasing, deaths have not increased significantly.

"Increases have been recorded among all age groups, but the highest number of cases are currently in the 10- to 14-year-old age groups," she said.

The sublineages have been found in seven of South Africa's nine provinces, as well as in 20 other countries around the world.

"There is quite a lot of diversity in this omicron family of lineages," Richard Lessells, an infectious disease specialist at the KRISP genomics institute, said on the call. This could explain why the newly identified sublineages are causing an upsurge of infections, he said.

Inputs from the Bloomberg