Promising news about Johnson & Johnson's COVID-19 vaccine candidate comes the day before Maryland opens its third mass vaccination site.|| Coronavirus updates | Maryland's latest numbers | Get tested | Vaccine Info ||M&T Bank Stadium -- especially around Gate A -- was abuzz with activity Wednesday as a crane, trucks, golf carts were used to install massive signs spelling out where to go for the state's third mass vaccination site set to open Thursday."It feels good. It feels good to help out and be a part of what's going on," said George Wine, with ARK Signs. "Everybody has to do their part, whether it's putting up the sign or the National Guard setting up the barricades, everybody has to do their part."Maryland online vaccination site locatorVaccine Data DashboardMaryland vaccination plan FAQsMilitary and medical staff were seen preparing the site for its launch."I thought that the teamwork was pretty great. I have never seen anything like this. I like how the Baltimore community came together," said Yesenia Fuentes, a nurse with the University of Maryland Medical Center. "(We're) up and running in no time and I'm so excited to see what the great things are that are going to come out of this."Thursday is a soft launch for the site. By next week, health officials said they'll be administering 2,000 shots a day at the stadium site, but they could do 10,000 a day if they had the had the doses. That's why this early green light for the J&J candidate is seen as such good news."There's high protective efficacy against severe disease with the Johnson & Johnson," said Dr. William Moss, executive director of the Johns Hopkins Bloomberg School of Public Health's International Vaccine Access Center. The preparation comes as the J&J single-dose vaccine candidate took one step closer to federal approval for emergency use. The Food and Drug Administration on Wednesday said the J&J COVID-19 vaccine, which is produced in Baltimore, appears to be safe and effective."The implication of that is that we would have now a third vaccine for which there's an emergency use authorization in the United States," Moss said.According to the FDA briefing, the J&J shot has 72% efficacy against all COVID-19 in the United States, it's 86% effective against severe forms of COVID-19 in the United States and it's 66% effective against all COVID-19 variants worldwide. The results are after one dose."I would say that's at least as good, if not better than many flu years, and remember, the FDA at the beginning of all this process said they would issue emergency use authorization if the vaccine had 50% efficacy or higher," Moss said.Moss said there is an ongoing trial in the U.S. looking at two shots, and he expects the two-shot regimen will have higher efficacy."This is after one dose, so there are advantages, particularly in certain populations, of a single dose of a vaccine," Moss said. "The data that were released today suggests perhaps milder side effects after one dose of the Johnson & Johnson vaccine. We'll have to see how that plays out."