What if the vaccine is more or less useless in fighting the omicron, and whatever comes next? The vaccine was 10% less effective with the delta variant, and the vaccine is 40% less effective with the omicron. Is that 40% of 100% or 40% of 90%?
Either way, is the vaccine making a significant difference regarding stopping the virus? In the olden days, pre-2020, vaccine meant never getting the illness. Now it means percentage of effectiveness against illness. The language alone is confusing.
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The flu vaccine doesn't mean never getting the illness, but it does reduce the chances of getting seriously ill. They aren't able to always predict the actual strain that will be circulating when they develop the vaccine ahead of flu season.