The omicron subvariant BA.2.12.1 is poised to become dominant in the US, currently accounting for an estimated 36.5 percent of all US SARS-CoV-2 cases, according to the latest estimates released Tuesday. by the Centers for Disease Control and Prevention.
The rise in the subvariant is the latest rapid succession of omicron subvariants, from the skyrocketing peak of cases of the initial omicron subvariant BA.1 in January to the current bump caused by the subvariant BA.2, gaining dominance in March. reached. As before, the reason for the viral usurpation is that ommicron subvariants continue to develop advantages: BA.2.12.1 has a transmission advantage over BA.2, which had a transmission advantage over BA.1, which had a significant advantage over BA. from delta.
The imminent reign of BA.2.12.1 raises concerns about yet another wave of infections and raises questions about how effective future omicron-specific vaccines might be against symptomatic infections.
The good news so far is that current vaccines still provide strong protection against severe COVID-19, and BA.2.12.1 does not appear to cause more serious illness than BA.1 or BA.2 — although the CDC and other health agencies experts actively monitor this. However, the subvariant appears to be able to evade immune protection, particularly that of previous BA.1 infections.
evasion
In preliminary data posted online Monday, researchers in Beijing found that BA.2.12.1 showed “strong neutralization evasion” against antibodies from vaccinated people who had also had breakthrough BA.1 infections. In the study, participants were vaccinated with Sinovac’s CoronaVac vaccine, an inactivated whole-virus vaccine, which was about 50 percent effective in early observational studies in Brazil. (mRNA-based vaccines showed efficacy rates of about 95 percent in initial clinical trials.)
The researchers looked at neutralizing antibodies from 50 people who had received three doses of CoronaVac and recovered from a BA.1 infection. When comparing neutralizing antibody levels across a range of coronavirus variants, researchers found that neutralizing antibody levels against BA.2 were approximately 1.86 times lower than for BA.1. But things got worse when researchers switched to newer subvariants: The levels of neutralizing antibodies were 3.73 times lower for BA.2.12.1, compared with BA.1, and eight times lower for BA.4 and BA.5.
The latest finding mirrors that of preliminary data from South Africa, which Ars reported Monday. There, researchers found that in unvaccinated people who had recovered from BA.1 infection, neutralizing antibody levels were 7.6-fold and 7.5-fold lower against BA.4 and BA.5, respectively, compared with levels against BA.1. While vaccination with a Pfizer/BioNTech vaccine or a J&J vaccine narrowed the gap in neutralizing antibody levels, researchers still saw a loss in protection: 3.6-fold and 2.6-fold lower neutralizing antibody levels against BA.4 and BA, respectively. BA.5, compared to BA.1.
Taken together, the data all point to the possibility of more reinfections from newer omicron subvariants, especially in people who have not been vaccinated or are unaware of their vaccinations. This could spark even more waves of contamination in the US and around the world, although experts don’t expect another skyrocketing wave like the BA.1 peak in January.
To care
It also raises concerns about second-generation vaccine designs, some of which may target BA.1, at least in part. Last month, for example, Moderna announced it believed a bivalent vaccine — targeting two versions of the virus at once — would be a winning strategy for providing broader, longer-lasting protection.
“Our latest bivalent booster candidate, mRNA-1273,214, which combines the currently authorized Moderna COVID-19 booster with our [BA.1] ommicron-specific booster candidate, remains our lead candidate for the Northern Hemisphere booster in the fall of 2022,” said Stéphane Bancel, CEO of Moderna, in a statement at the time.
But the new data suggest that BA.1-based vaccines may provide weak protection against BA.2, BA.4, BA.5 and other ommicron subvariants down the line.
“Unlike when omicron first appeared, now omicron sublines have come to target humoral immunity [antibodies and other adaptive responses] caused by omicron itself, including the humoral immunity caused by post-vaccination omicron infection,” the authors of the new Beijing study write. “This presents a major challenge” to achieve protection and “suggests that a Omicron BA.1-based vaccine may not be the ideal antigen for inducing broad spectrum protection against emerging ommicron sublines.”
