Omicron, the major driver of COVID-19 infections around the world at present, has more than 50 mutations in its genome and is highly transmissible compared with previous variants. Some of Omicron’s mutations allow it to evade antibodies induced through prior infection, vaccination and antibody therapies.
So scientists got to work designing slightly adjusted formulations of the vaccines which would not only target the original strain of SARS-CoV-2, but newer variants of the virus too – Omicron in particular. These are called bivalent vaccines.
Because they were based on the same mRNA technology used in first-generation COVID-19 vaccines, they could be tested and approved quite quickly. But now we’ve been using bivalent boosters in the real world for a few months, we’re starting to gather some evidence on how well they’re working against Omicron.
UPDATED MRNA VACCINES
Both Moderna and Pfizer/BioNTech have updated their mRNA vaccines to provide broader protection. These vaccines contain small chains of genetic material known as messenger RNA that give instructions to our cells to make copies of the coronavirus spike protein.
Once these spike proteins are made, they’re used to train our immune cells to recognise and kill SARS-CoV-2 if we’re infected. The bivalent vaccines contain two types of messenger RNA molecules that provide the instructions for two different types of the virus spike protein: One from the original SARS-CoV-2 strain and another from Omicron BA.1.
A subsequent update has targeted Omicron BA.4 and BA.5, seeking to help our immune systems keep up with the rapidly emerging Omicron subvariants. It was hoped that these updated bivalent vaccines would train our immune systems to produce antibodies that can protect against Omicron and future variants that might emerge.
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