An infectious disease researcher explains how people reach 95 percent immunity, when it's safe to see friends and family again, when we'll move to a new normal and more.

Julie Mazziotta
January 16, 2021
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A person in the U.K. receives Pfizer's COVID-19 vaccine
| Credit: FRANK AUGSTEIN/POOL/AFP via Getty

After a month of fits and starts, state and local governments across the U.S. are slowly ramping up distribution of COVID-19 vaccines. Health care workers and nursing home residents were the first to roll up their sleeves for a dose, and several cities have since expanded to inoculating essential workers like teachers and grocery store employees.

But as more people become eligible for a vaccine, there is still some confusion about how much protection it gives early on, as well as when people will be at peak immunity from COVID-19. Here, infectious disease clinical researcher Laurel Bristow clarifies the process.

How does each vaccine work?

The two approved vaccines in the U.S., from Pfizer and Moderna, are both mRNA vaccines, a new (but highly researched) type of vaccine that teaches the body's cells how to make a spike protein that will create an immune response to fight off the spike protein from a virus, in this case COVID-19. Both vaccines require two doses to be fully effective — in Pfizer's case, that second dose is given three weeks after the first, and for Moderna, it comes four weeks later.

Both doses are needed to reach peak immunity, Bristow says.

"Your first dose trains your immune system to respond to the spike protein. And then the second dose is the booster to make sure that it can mount a really strong immune response, if the virus is introduced to the body," she says.

President-elect Joe Biden receives his second COVID-19 vaccine on Monday
| Credit: Alex Wong/Getty

How much protection does each dose provide?

After one dose of either Pfizer or Moderna's vaccine, a person has around 50 percent immunity to COVID-19, and the second dose brings it up to about 95 percent.

Is each dose immediately effective?

Not quite — the body needs time to build up its response.

"Your immune system starts to kick in, but to really get to the peak efficacy that we all know as 95 percent, it's going to take two weeks after your second dose," Bristow says. That means that people who get the Pfizer vaccine can expect to be at 95 percent immunity five weeks after their first injection, and those with Moderna will reach that point six weeks later.

Can you still get COVID-19 after a first or second dose of a vaccine?

Yes, because "your protection doesn't happen immediately," she says. "It's going to take two doses in time to get to the 95 percent efficacy. And especially after the first dose, it's not going to happen immediately that you are then protected from symptomatic COVID."

That's why there are reports of people contracting COVID-19, even after getting their first dose of a vaccine.

"It's been frustrating seeing those stories from a science communication standpoint, because those are happening within the first week of someone getting their first dose," Bristow says.   

Can I stop wearing a mask and see friends and family again after I'm fully vaccinated?

Unfortunately, not yet.

"We need to keep wearing masks to protect the people around us," Bristow says. "There's still a question of if the vaccine stops transmission of COVID, or just stops people from getting symptomatic COVID. That's something that is being looked at right now, so we want to operate under the assumption, just out of pure safety, that vaccinated people could still get asymptomatic COVID and spread it to others."

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Plus, she says, while 95 percent protection from the vaccine is great, "that 5 percent of possibility is a lot bigger when COVID-19 is spreading rapidly across the country."

But Bristow says she "might be a little bit less anxious" in some scenarios after she's fully vaccinated, "like if I'm around other people who are also vaccinated, because it means that our risk to each other is going to be lower."

When will the country be back to some sort of "normal"?

"The goal is for that to happen by mid-summer," Bristow says, but the U.S. is currently well behind their targeted goals for vaccinations. The Trump administration fell far short of its promise to vaccinate 20 million Americans by the end of December, instead reaching just 2.7 million. President-elect Joe Biden has stated that he wants 100 million doses given in his first 100 days in office, "but the issue is vaccine rollout and vaccine hesitancy, and being able to actually get shots in arms to get transmission down enough for us to start feeling normal again," Bristow says.

How is vaccine distribution going?

The Trump administration left vaccine distribution up to individual states and local governments, leading to a disjointed rollout with most areas lacking the infrastructure to give out the vaccine to citizens. Plus, both vaccines have to be kept frozen until they're ready for use, and once they thaw they cannot be refrozen, leading injection sites to toss unused doses that will soon expire.

"You really need to make sure that you're thawing the appropriate number of vaccines for people who will be getting them," Bristow says.

With doses going unused, the approach to vaccine distribution is changing. The Trump administration initially wanted to hold back vaccine doses to ensure that each vaccinated person has a guaranteed second dose. But with it looking like Pfizer and Moderna will be able to ramp up production and have more doses available, and Biden pushing for it, the White House said Jan. 12 that it will release all doses now to get as many people vaccinated as possible.

Is it fair that some states are allowing teachers to get vaccinated before health care workers in other areas?

"I think right now the priority should be to use vaccines before they expire," Bristow says. "Some organizations are better suited and have better logistics and were ready for vaccine distribution more than others, and so they are able to then move on to other groups before some priority groups in a different state or a different jurisdiction have gotten what they need. It doesn't really make sense, if you are in a position to vaccinate more people in lower risk groups, to wait until the other areas catch up."

The goal right now is to get as many people vaccinated as possible.

"It's important to get vaccinated for yourself and others," she says. "If you look at Los Angeles right now, COVID is a huge burden on the healthcare system and on people's lives with ICUs being overwhelmed because of uncontrolled community spread. It's really important that we do what we can to limit transmission of COVID and also to protect ourselves and others, and we can do that by getting vaccinated."

The situation surrounding COVID-19 continues to change quickly; it's possible that information or data has changed since publication. While EatingWell is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations by using the CDCWHO and their local public health department as resources.

This story originally appeared on people.com