(CNN) On Tuesday, the US Food and Drug Administration gave the green light to Americans 50 and older to receive an additional Covid-19 booster shot . Here's what we know about how effective the fourth dose appears to be: Israel, as has happened numerous times through the pandemic, has led the exploration of whether the fourth dose is beneficial to protect against Covid. The good news: Antibody levels jumped nicely; the no news: There was only a trivial reduction in clinical illness among the fourth dose recipients. And it demonstrates the benefit for a distinctly older age group: Two-thirds of all deaths were among those older than 80 years of age. If the fourth dose is very effective in the very old, effective in the old and not-so-effective in the not-so-old, the human immune system probably is telling us something.

Source: CNN April 04, 2022 02:12 UTC