The COVID-19 pandemic

[plam]

This is why seniors can now receive an extra-strength dose.  I believe todays vaccines also offer protection against more than one strain.  I do recall that, a few years ago, they got the strain wrong and the vaccine that year was not very effective.

Nostradamus allegedly said, “Prediction is difficult, especially about the future."

And that's what they do with flu vaccines: they try to anticipate which flu strains will be predominant over the coming season. There is no way to know the correct answer at that time, all you can do is try to use your knowledge of prior patterns.

However we did seem to have eradicated one of the strains that was circulating pre-pandemic: https://www.webmd.com/lung/news/20211025...tinction#1

The wrong prediction will probably still give some protection, but much less than the not-awesome protection from the right prediction.