The XBB.1.5 variant is the most contagious discovered to date, but is it also a champion of immune escape? A pre-publication delivers the first elements of an answer as to the effectiveness of available vaccines against this umpteenth variant of Omicron.
XBB.1.5, or the “Kraken” as a Canadian biology professor dubbed it who would like to see SARS-CoV-2 variants renamed after monsters from Greek mythology, is very contagiouscontagious but does it escape our immune defences? For each new variant detected, scientists must answer this crucial public health question.
Escape from the “Kraken” variant antibodies
The data available for XBB.1.5 is still very incomplete. A preprint on BioRvix tackled this question by studying the immune responseimmune response cellular and humoral of 30 volunteers who received a booster dose of a bivalent RNA vaccine from Pfizer or Moderna, designed to fight against variants ofOmicronOmicron. Their serumserum was sampled and brought into contact with virus-like particles mimicking the XBB.1.5 variant to test the neutralizing properties of antibodyantibody and, in a second test, the effectiveness of lymphocyteslymphocytes T.
Unsurprisingly, XBB.1.5 escapes neutralizing antibodies, but in similar proportions to what was observed for XBB.1. The F486P mutation located in the proteinprotein S makes it highly contagious but does not increase its immune escape. The cross-reactive T lymphocytes remain always active against XBB.1.5. The preprint also points out that the booster dose is only effective for three months, after which the amounts of neutralizing antibodies fall back to their pre-booster level. Even if its effectiveness decreases quickly, the vaccine booster dose is the most effective and safe way to protect against the appearance of new variants of SARS-CoV-2.
