https://www.siliconvalley.com/2021/08/06/moderna-vaccine-is-durable-through-6-months-booster-needed-by-winter-says-company/ > Moderna’s mRNA coronavirus vaccine remains at a high 93% efficacy for six months after the second dose, but company officials said a booster shot will likely be needed by winter due to the delta variant and seasonality of the virus. > The Cambridge-based biotech company announced its six-month data on Thursday, which also showed Phase 2 trial studies of three different Moderna booster shots that triggered antibody responses against coronavirus variants including the ultra-contagious delta variant.