#16,840
Over the past few weeks we've looked a steady procession of studies and risk assessments (see below) warning that the BA.2.12.1, BA.4, and (rapidly rising) BA.5 variants all enjoy enhanced immune escape characteristics, making the COVID vaccines (and boosters) and prior infection less protective than they were against BA.1 and BA.2.
Nature: Immune Escape Properties of BA.2.12.1 & BA.4/BA.5
SSI: Risk Assessment on BA.2.12.1, BA.4, and BA.5 Omicron Subvariants
ECDC: Implications of the Emergence and Spread of Omicron VOCs BA.4 and BA.5 for the EU/EEA
Preprint: Virological Characteristics of the Novel SARS-CoV-2 Omicron Variants including BA.2.12.1, BA.4 and BA.5
While there is no current evidence that BA.4 or BA.5 produce any more severe illness than BA.1 or BA.2, their ability to evade prior immunity is expected to result in more infections, and a rise in hospitalizations and deaths, as they take control.
Vaccination (and boosters), along with prior infection, are still expected to reduce the severity of COVID illness, even if they provide relatively little protection against infection.
To above list we can add a brief correspondence, published yesterday in the NEJM, from researchers at Beth Israel Deaconess Medical Center, Harvard Medical School, who report a substantial drop in neutralizing antibodies (from either prior infection of vaccination) against the Omicron BA.4 and BA.5 subvariants.
Specifically, they report - when compared to the 2020 Wild-type virus - the vaccine's neutralizing antibody titers were:
- lower by a factor of 6.4 against BA.1;
- by a factor of 7.0 against BA.2;
- by a factor of 14.1 against BA.2.12.1;
- and by a factor of 21.0 against BA.4 or BA.5.
Neutralization Escape by SARS-CoV-2 Omicron Subvariants BA.2.12.1, BA.4, and BA.5June 22, 2022DOI: 10.1056/NEJMc2206576
The authors sum up their findings by stating:
These data show that the BA.2.12.1, BA.4, and BA.5 subvariants substantially escape neutralizing antibodies induced by both vaccination and infection. Moreover, neutralizing antibody titers against the BA.4 or BA.5 subvariant and (to a lesser extent) against the BA.2.12.1 subvariant were lower than titers against the BA.1 and BA.2 subvariants, which suggests that the SARS-CoV-2 omicron variant has continued to evolve with increasing neutralization escape.
With just over 50% of cases in the United States estimated to be BA.2.12.1, and BA.4 and BA.5 rapidly gaining ground (now estimated at about 36% combined), hospitalization are already rising, and a summer wave of COVID seems all but guaranteed.
COVID's ability to reinvent itself, with progressively immunity-evasive variants, makes if very difficult to predict where this pandemic goes next.
