Do bivalent boosters work against XBB.1.5? Vaccine questions, answered. – The Washington Post

Coronavirus boosters are sparking confusion and questions again as the United States confronts the growth of a new variant adept at evading immunity, while federal officials consider switching to an annual shot model.

The XBB.1.5 variant is a highly transmissible descendant of omicron that is now estimated to cause about half of new infections in the country. Early lab studies showed that it was especially effective at evading virus-fighting antibodies, prompting concerns that it might more readily slip past the updated boosters.

But a new study released Wednesday by the Centers for Disease Control and Prevention offers reassurance that the updated booster shots, which rolled out in the fall, are still protecting people in the real world.

The new booster shots are bivalent, meaning they are designed to protect against both the original strain and the BA.5 omicron subvariant that caused most infections over the summer. The latest data shows that the booster protects people from getting sick with XBB.1.5 about as well as it did against BA.5.

The CDC data arrived around the same time that the Food and Drug Administration is considering switching the country’s vaccine strategy to mimic the one used for the flu, with people getting annual shots targeting whichever strain is predicted to dominate during the fall and winter.

Amid a swirl of new information, The Washington Post received hundreds of questions about booster shots for a recent reader live chat with health reporters and CDC Director Rochelle Walensky. Here’s what we know and don’t know about boosters.


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