Ricardo Palácios, medical director of clinical research at Butantan, said the lower efficacy rate (of Sinovac Vaccine 科興) was caused by the inclusion of patients who were infected with the novel coronavirus but only displayed “very light” symptoms.
Phase 3 trial data for the US-based Pfizer-BioNTech Covid-19 vaccine, for example, gives a 95 per cent efficacy rate. The 44,000 volunteers, all of whom had tested negative for Covid-19, included 3,410 participants who displayed Covid-19 symptoms and were not included in the total efficacy rate, according to a US Food and Drug Administration report. In the unlikely event that all of those 3,410 had been false negatives, the total efficacy rate would drop to below 30 per cent.