"Convalescent serum studies suggest natural antibodies are less effective", Abdool Karim said, introducing the research, "(but) current data suggest the new variant is not more severe".
This comes after the UK's chief scientific adviser Sir Patrick Vallance told Sky News that coronavirus variants were a "real issue of concern".
Bishal Bhandari, Senior Epidemiologist at GlobalData, comments, "This new strain is independent of the UK's new strain, but the mutation and rise in cases in South Africa had gone largely unnoticed, especially in the earlier stages, while extensive coverage was given to the new United Kingdom variant, SARS-CoV-2 (B.1.1.7), which is believed to have caused the spike of cases in the UK".
It is one of several new variants discovered in recent months, including others first found in England and Brazil.
"It also shows we urgently need to find out if we could see infection with this variant post-vaccination". However, a 23% week-on-week drop in the number of reported new infections is cause for optimism, he said.
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Preliminary findings by scientists at Public Health England (PHE) showed that reinfections in people who have COVID-19 antibodies from a past infection are rare. Researchers took blood samples from 16 people who had received the vaccine and exposed the blood to a synthetic virus, or pseudovirus, that was engineered to have 10 mutations found in the United Kingdom variant.
The findings are "not good news but it's not unexpected", said James Naismith, Director of the Rosalind Franklin Institute, in comments to the Science Media Centre.
"The vaccines do stimulate very strong responses, immunity is a sliding scale, it's not an on/off switch", he added. AstraZeneca Plc, Moderna Inc and CureVac NV are also testing whether their respective vaccines will protect against the fast-spreading variants. Study results are expected within the next week or two.
The authors tested the United Kingdom strain in the laboratory with antibody-rich blood plasma from 36 patients who had recovered from either mild or severe forms of Covid-19 and found most were able to neutralise the variant. When researchers tracked outcomes of 8,515 COVID-19 patients admitted to 88 U.S. Veterans Affairs hospitals in 2020, they found that survival rates improved between March and August.