(NEXSTAR) – Depending on when you last got vaccinated, that COVID-19 shot may no longer be a good match for the variants expected to dominate this fall and winter.

As a virus circulates, it continues to mutate. Some mutations can make it spread faster, others make symptoms feel stronger, and some changes make it better at evading your pre-existing immunity.

This year's new batch of shots, reformulated and released over the past two months, are a "fairly good match" to the predominant variants infecting people right now, said Dr. Andrew Pekosz, professor at Johns Hopkins Bloomberg School of Public Health, in a recent media........

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