Growing unrest about new Omikron peak in South Africa

In South Africa, there has been a rapid increase in the number of infections with two new subtypes of the Omikron variant of the corona virus for the past two weeks. It concerns types BA.4 and BA.5. They seem to escape defenses against the earlier subtype that circulated in South Africa (BA.1). Virologists had been closely monitoring the variants for weeks, but until recently there was no reason to raise the alarm. The infections in South Africa did not lead to an increase in hospitalizations or deaths from Covid-19 until recently. But since a week hospital admissions are increasing again in some South African provinces, reports bioinformatician Tulio de Oliveira, director of the Center of Epidemic Response and Innovation at Stellenbosch University in South Africa. The number of registered infections in South Africa is now back to the same level as at the beginning of December, just before the fourth wave.

Clear advantage

“Alarm is a big word, but these sub-variants clearly have some advantage,” says virologist Marion Koopmans of Erasmus MC. “It looks like they’re going to create a new wave in South Africa.”

Since the Omikron variant of the coronavirus was discovered in South Africa on November 26, it has supplanted all others worldwide. Omikron is much more contagious than previous variants and partly escapes previously built up defenses. There were initially three subtypes, BA.1, 2 and 3.

In South Africa, it is estimated that at least 90 percent of the population has built up immunity to the coronavirus – some through vaccination, but the vast majority of people through a previous infection. But after three months, the strength of that defense wanes – it is no coincidence that the spread of the new subtypes started about four months after the start of the fourth wave in South Africa, mainly caused by BA.1.

Avoiding defenses

Because the new subtypes BA.4 and BA.5 also seem to evade the immune system due to new mutations, they are now quickly gaining a foothold in South Africa. It will the severity of BA.4 and BA.5 varies by country or regiondepending on how the defenses are built up on the spot, De Oliveira thinks.

Scientists are trying to find out as soon as possible to what extent these new subtypes escape the immune system, and whether they are more sickening than the earlier Omikron subtypes. The first data on the defense published the South African virologist Alex Sigal this week in a preprint† This gives the impression that the virus-neutralizing antibodies that (unvaccinated) people have after an infection with BA.1, are more than seven times less effective against BA.4 and BA.5. The antibodies of people who had been vaccinated (with Pfizer or Janssen) and who received an infection with BA.1 on top of that held up better: they worked three times less well.

Researchers are still in the dark about how sickening the new subtypes BA.4 and BA.5 are. “The first subtypes of Omikron were clearly milder than previous variants, Alfa, Beta and Delta,” says Koopmans. “It is not yet clear whether these new subtypes are comparable to the first Omikron, or to Alfa or Delta. That question is also becoming increasingly difficult to answer, because the circulating variants and the structure of the defense system are different in every country.”

Twenty countries

Small numbers of these BA.4 and BA.5 subtypes have already been picked up in more than twenty countries, including Australia, the United States, China, Israel, Austria, Belgium, Germany, France, Denmark and the United Kingdom. In the Netherlands they have not yet been found in the weekly samples of general practitioners and test streets, BA.5 was found once in early April in another study. In our country, BA.1 mainly circulated in December and January, the subtype BA.2 has been dominant since mid-February.

We have to wait and see what BA.4 and BA.5 will mean in Europe and in the Netherlands, says Koopmans. “It’s too early to make any statements about that.”

The source of the new subtypes is still a mystery. “They did not arise from the earlier Omikron subtypes, but all appear to have evolved from the same source. This could be, for example, someone with a bad immune system, who therefore carries the virus for a long time, or a certain animal species,” says Koopmans.

Never a dull momentKoopmans says. “But it again underlines that we really need to have long-term plans. We have just scaled down testing and surveillance, which is not wise. I also really want to get rid of it, but this virus continues.”