In April, more than half the samples sequenced in South Africa were reported as BA.4 and BA.5
South Africa is currently in the middle of what many believe to be the start of its fifth COVID-19 wave. Omicron sublineages BA.4 and BA.5 are likely driving this surge, which began two weeks ago.
On May 1, 2022, South Africa recorded more than 4,000 new cases, according to private aggregator Our World in Data. The country witnessed a total of 3.7 million confirmed infections and over 100,000 deaths during the pandemic — the highest in the continent.
Health minister Joe Phaahla said in a press conference April 29, 2022:
What remains stable ... is hospital admissions, including intensive care units (ICUs), not a very dramatic change. There was also a rise in deaths, not very dramatic from a low base.
The country’s omicron wave began in November 2021 and dissipated by January this year, according to the National Institute For Communicable Diseases Of South Africa. By March, BA.2 — what was for long referred to as the ‘stealth variant’ — was dominating. It caused an increase in cases but didn’t trigger a new wave, and just prolonged the tail end of the spike caused by omicron.
In April, more than half the samples sequenced in South Africa were reported as BA.4 and BA.5 with their presence beginning to increase from early March itself, data presented by the country’s health ministry showed.
BA.4, which was first sequenced on January 10 in Hong Kong, and BA.5, l which was first sequenced on 6 January in South Africa, have eight and 11 additional mutations respectively as compared to BA.2.
Till the end of April, some 402 cases of BA.4 and 179 of BA.5 were identified across the globe, according to outbreak.info, a platform that aggregates data across scientific sources, provides tools to track COVID-19 cases, deaths, variants and collate research on the virus.
The World Health Organization (WHO), in its weekly epidemiological update on April 27, had stated that evidence till now does not indicate differences in severity or clinical manifestations of a BA.4 / BA.5 infection.
“The impact of each single mutation or computation of mutation (is) difficult to predict. Work (is) underway to understand how these changes affect the virus properties (particularly how well it evades immunity and whether it changes disease severity,” the country’s health agency said.
The rise in cases in South Africa is among the three key areas of concern, according to the latest projections by the Institute for Health Metrics and Evaluation (IHME), an independent population health research centre at the University of Washington Medicine.
It has now been about four months since the omicron wave peaked in the country. “The question remains — is that because these sub-variants are more transmissible, or is it because they have immune escape over BA.1 and BA.2, which were there in South Africa and had become the predominant variants, or is it because of waning immunity, just through time,” IHME posed the question.
The population in South Africa has mixed immunity, acquired from vaccines and infections during previous waves triggered by beta, delta, omicron and its sublineages. Only 31 per cent of the population has completed its initial vaccination protocol, according to Our World in Data.
BA.4 and BA.5 cases are on the rise and so, it is likely that they can cause reinfection, said SA’s health agency. This may particularly be the case for those infected with BA.1 since the two new sub lineages are markedly different from this. A waning immunity could also be contributing to this surge.
In a study, which is yet to be peer reviewed, scientists found that those infected with BA.1 recorded an eight-fold drop, while those vaccinated recorded a three-fold decrease in neutralising antibodies when tested against BA.4 and BA.5.
“The low absolute neutralisation levels for BA.4 and BA.5, particularly in the unvaccinated group, are unlikely to protect well against symptomatic infection, the study noted. This may indicate that, based on neutralisation escape, BA.4 and BA.5 have potential to result in a new infection wave, it added.
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