Getting through an initial omicron infection may not save you from the sub-variants of omicron, according to preliminary data from South Africa.
The country is currently on the cusp of a new wave of infections, primarily driven by two ommicron coronavirus sub-variants, BA.4 and BA.5. Despite a skyrocketing wave of cases of the first BA.1 omicron variant in December that infected much of the country, the number of new omicron cases has risen 259 percent in the past two weeks, according to data recording by The New York Times. The number of hospitalizations has also risen and the number of deaths has increased by 18 percent.
Preliminary data posted online last week help explain why cases are on the rise again — the BA.4 and BA.5 omicron subvariants can evade neutralizing antibodies generated by infections of BA.1. For the study, led by virologist Alex Sigal of the Africa Health Research Institute, researchers compared neutralization antibodies from people infected with BA.1 with BA.4 and BA.5 in a lab. They had samples from 24 unvaccinated people infected with BA.1 and 15 vaccinated people who also had BA.1 infection (eight people had been vaccinated with the Pfizer/BioNTech vaccine and seven had the Johnson & Johnson vaccine). vaccine).
For the unvaccinated humans, the neutralizing antibody levels were 7.6-fold and 7.5-fold lower against BA.4 and BA.5, respectively, compared to the levels against BA.1. In vaccinated humans, the decline was shorter: 3.6-fold and 2.6-fold lower against BA.4 and BA.5, respectively.
Always evolving
Although the study is small and the data is preliminary, the findings suggest that the latest omicron subvariants may thwart the protection generated by earlier omicron versions. Vaccination, however, seems to extinguish the fringe of the subvariants. Total neutralization levels against BA.4 and BA.5 were five times higher in vaccinated people compared to those who had not been vaccinated.
Still, in places where vaccination coverage is low or vaccine protection is declining, BA.4 and BA.5 could generate a new wave of cases, as appears to be the current situation in South Africa.
In the US, where vaccination coverage is relatively high but protection may be on the wane, BA.4 and BA.5 have so far only been found in low concentrations. For now, another sub-variant, BA.2, dominates, which is currently causing a rise in the number of cases. BA.2 is similar to BA.4 and BA.5 – BA.2 differs from BA.4 and BA.5 by only three mutations and one deletion in the virus’s critical spike protein.
But US experts are closely monitoring another subvariant, BA.2.12.1, which has a similar mutation profile to BA.2, but two additional mutations† One of the mutations in BA.2.12.1 is co-located with a unique mutation in BA.4 and BA.5: amino acid position 452.
While BA.2 is still the dominant variant in the US, BA.2.12.1 is quickly gaining ground. Currently, BA.2 accounts for an estimated 68 percent of SARS-CoV-2 cases in the US, and BA.2.12.1 accounts for an estimated 29 percent, according to the Centers for Disease Control and Prevention.
