Explainer | The latest coronavirus boosters target Omicron. Are they safe and effective?
- FDA has authorised emergency use of Pfizer-BioNTech and Moderna boosters that target BA.4 and BA.5 variants of Omicron
- Shots based on original strain still offer protection but the rapid virus evolution means newer variants can dodge protective antibodies they induce
This is the first major revamp of Covid-19 vaccines since they were rolled out in December 2020. The boosters, which only went through animal trials and were not tested on humans, have been backed by the US Centres for Disease Control and Prevention, and are expected to be made available to the public in early September.
Here is what you need to know about the updated bivalent booster doses.
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Why do we need bivalent vaccines?
The vaccine shots based on the original strain still offer protection against severe illness and death, but the virus has evolved so much and so fast new variants are able to dodge the protective antibodies induced by the vaccines. As a result, the effectiveness of different vaccines in preventing infection and mild illness has declined substantially. In June, an advisory committee of the US Food and Drug Administration (FDA) voted to include an Omicron component in the new Covid-19 booster vaccines.
They are called bivalent vaccines because they contain two messenger RNA (mRNA) components of Sars-CoV-2 virus – one that was found in the early stages of the pandemic in Wuhan in central China and the basis of vaccines currently in use, and the other BA.4 and BA.5 strains. The latter two have identical spikes.
Public health officials believe the redesigned boosters will provide more lasting protection against the virus and reduce hospital admissions this autumn and winter.
Who should be eligible for them?
