Pfizer booster shows positive results against Covid-19
In a presentation, posted on the Food and Drug Administration (FDA) website, Pfizer says real-world data from Israel and the US suggest that in the context of the Delta variant “vaccine protection against Covid-19 infection wanes approximately 6 to 8 months following the second dose”. The decrease in effectiveness is “primarily due to waning of vaccine immune responses over time”, rather than the Delta variant.
Giving a third dose to people older than 60 was associated with 86% effectiveness against testing positive for Covid-19 starting at least a week after the booster. Pfizer also detailed immune response results from a final-stage trial of booster shots in over 300 people, showing that a month after the third dose, levels of the protective antibodies were more than triple what they had been a month after the second shot.