For more than 10 months, we have endured COVID-19. We watched businesses struggling to survive and a nation behind masks with more than 275,000 dead in the U.S. from the virus.
But as a second spike spreads more havoc across the country -- a potential savior is arriving in the form of a new vaccine.
Still, many are questioning whether it will live up to its billing.
“Vaccines aren't going to save a single life, but vaccination is,” said Dr. George Rutherford.
What the UCSF infectious disease expert means by that is the success of the vaccine will depend on getting it to as many people as possible.
“Having the vaccine ready to go is terrific, you've got the cold chain and the logistics worked out, but it's gotta get in peoples' arms to make a difference,” said Rutherford.
Vaccine maker Pfizer said its COVID vaccine has 95% efficacy.
But what does that really mean? Here's how it works:
Say around half the vaccine test group was given a placebo -- and then exposed to the virus. In that scenario, 100% of the placebo group would get the virus.
But for the other half, given the actual vaccine and then exposed to the virus -- only 5% would get COVID-19 -- 95% would be immune.
“To have a vaccine that has an efficacy of 95%, that's remarkable. That's as good as our best vaccine,” said Rutherford.
So how many people have to get vaccinated in order to achieve “herd immunity?” A veterinary term describing what proportion of a herd of animals has to have immunity so a virus has nothing left to infect.
The idea behind herd immunity is that if others are immunized and you’re not, the virus has a harder time finding you. And if it does get to you, it has no place to go.
Rutherford says we've learned a lot about COVID and herd immunity by watching its rapid spread through places like San Quentin prison or on cruise ships.
“So we think that from those experiences, that herd immunity lies in the 70 plus percent” said Rutherford.
But achieving that 70% number won't be easy. There will need to be enough doses of the vaccine to inoculate 60-70% of the population. And then there will be some who will refuse to get it.
Rutherford says the science is complex, but the math is simple.
“And if we don't get a large enough proportion of people immunized, everyone's going to be walking around with masks this time next year,” Rutherford said.