Pfizer Inc. /zigman2/quotes/202877789/composite PFE -4.12% and German partner BioNTech SE /zigman2/quotes/214419716/composite BNTX -16.96% said Thursday a late-stage trial of a 30 mg booster dose of their COVID-19 vaccine showed efficacy of 95.6% compared with those who received a placebo. The companies said the Phase 3 trial involved more than 10,000 people aged 16 and older, who had already received the primary two-dose series, and found the booster restored vaccine protection against COVID to the high levels achieved after the second dose. The booster was found to be safe. "These important data add to the body of evidence suggesting that a booster dose of our vaccine can help protect a broad population of people from this virus and its variants," said Ugur Sahin, M.D., CEO and Co-Founder of BioNTech, in a joint statement with Pfizer CEO Albert Bourla. The companies are planning to submit the data to the Food and Drug Administration, the European Medicines Agency and other regulators around the world. Pfizer shares jumped about 1% premarket, while BioNTech was up 1.8%. Pfizer shares have gained 16% in the year to date, while BioNTech has gained 230.5%. The SPDR S&P Biotech ETF /zigman2/quotes/205950134/composite XBI +0.46% has fallen 12% and the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.51% has gained 21%.