Vaccines from AstraZeneca, Russia’s Gamaleya Institute and Johnson & Johnson fight the coronavirus with another virus, leaving scientists concerned the shots may lose potency if annual inoculations become necessary to fight new variants.
So-called viral vector shots — also used by several Chinese Covid-19 vaccine developers — use harmless modified viruses as vehicles, or vectors, to carry genetic information that helps the body build immunity against future infections.
However, there is a risk that the body also develops immunity to the vector itself, recognising it as an intruder and trying to destroy it.
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