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by astrange
1833 days ago
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It's typically because of the adjuvants added to vaccines, and some other mutations done for stability. The major covid vaccines have fewer adjuvants (to allow for boosters) and 2 shots because that's just how the trial was run, and it turned out to work, but later testing shows they're pretty effective just with one and some countries have been delaying the second one until everyone gets their first. |
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