In clinical trials, multiple leading COVID-19 vaccines were tested as a two-shot regimen. In the real world, three doses have proven to offer strong protection against serious illness. And now, in multiple countries, fourth doses are being explored as a way to ward off waning immunity.
So does that mean you should rush out and get another shot if the opportunity arises? Not necessarily.
The human immune system is a broad, multi-faceted defence network. It starts off rather immature in your infancy, typically sharpens as you age, and tends to struggle more to fight off pathogens in your golden years.
That’s
