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Vaccines: Herd Immunity, Passports, Reaching the Underserved

Three Duke experts examine pressing vaccination issues

Part of the The Briefing: The Impact of COVID-19 Series
Vaccines: Herd Immunity, Passports, Reaching the Underserved

DURHAM, N.C. -- As the COVID-19 vaccinations roll out with increasing speed, questions are now arising about herd immunity, the need to reach underserved populations, and a proposed passport program that would provide proof of a person’s vaccination record.

Three Duke scholars tackled these and other issues Wednesday in a virtual briefing for journalists.

Watch the briefing on YouTube.

Here are excerpts:


Dr. Emmanuel Walter Jr., chief medical officer, Duke Vaccine Institute

“The best estimates from all the experts we can see is approximately 70 to 85 percent of the population needs to receive a vaccine to achieve what we call herd protection. I like to actually call it community protection. That’s a pretty high bar to achieve. There are other infectious diseases, for example, measles, where we actually have to achieve closer to 95 percent coverage in the population, and we do pretty well with that.”

“We really have made some substantial and incredible progress over the past several months. We have 167 million doses of vaccine administered and about 107 million people have received a first dose. So how does that translate? About 33 percent of the population has received a first dose of vaccine and about 19 percent of the population now is fully vaccinated. That’s still a pretty big gap when you’re looking to try to achieve 75 percent in the population.”

“We’re making some really nice progress. We still have some room to go. The one particular population where we really achieved good coverage is those who are at highest risk in the oldest age group. If you look at people who are over 65 percent, 75 percent have received one dose of vaccine and 55 percent are fully vaccinated. That’s really good news.”

“The one group that I think we really need to add into the equation to achieve community protection … are children. I think, as you all know, clinical trials for children are well underway. Children make up about 23 percent of the population. So if you automatically discount vaccinating children you’re already down to about 75 percent or so of the population that’s getting vaccinated if you don’t vaccinate children. So reaching our goal to achieve herd immunity, I think we need to consider vaccinating children.”


Lavanya Vasudevan, family medicine and community health professor

“Compared to December when the vaccines were first approved, we have doubled the proportion of U.S. adults willing to be vaccinated. The majority of the shift in willingness to be vaccinated is driven by the high efficacy of the vaccines and their safety profiles. Many people who initially wanted to wait and see how the vaccines turned out are now willing to be vaccinated.”

“Still, one of the biggest hurdles is with vaccine access and making sure everyone who wants to get vaccinated is able to do so. Although about 60 to 65 percent of U.S. adults want the vaccine, only half have received one dose of the vaccine so far.”

“We know challenges with vaccine access and appointment scheduling can create frustration and reduce trust in the vaccination program. We need to make sure we have the ability to provide vaccines to everybody who is eligible.”


Nita Farahany, professor of law, philosophy

“People are anxious to get back to some sense of post-pandemic normal. Going to a restaurant. Getting on an airplane. Or even gathering with people in groups in places indoors where we haven’t been able to do so … people think a vaccine passport … would give them a greater sense of security.”

“That could be a big boost to the economy. It could give people a sense of safety and an ability to re-engage.”

“There are a lot of risks, though, to adopting this kind of vaccine passport approach.”

“The moment at which it might be ethical to adopt it is the moment when we might not need them anymore.”

“We’re starting to develop data that shows people who are vaccinated are unlikely … to get infected themselves, therefore unlikely to spread it to other people. But there’s still a risk. If people get the sense there’s no risk of infection, they may unwittingly start to let down their guard in ways that are particularly dangerous.”

“(There is) an equity concern. You’ve heard already about the distribution of the vaccines. We’re getting there. We’re doing a great job of starting to roll it out. But notice the way we prioritize vaccination wasn’t by the people who were economically hit the hardest by the pandemic. Instead it was the people most vulnerable to serious disease or death.”

“If we had been able to contain the virus more, we might have had a different strategy where you would distribute it to people most likely to be out and about spreading it to other people in society. Or you might have chosen to distribute it to the people who were most economically harmed and therefore need to be able to re-integrate into society more quickly.”

“If we condition participation in society based on access to a vaccine passport, and we do so now, at this moment, when at least half the U.S. population don’t have access to the vaccine … then what you’ll see is a widening gap. Jobs lost to the pandemic will go to people who were able to gain earlier access to the vaccines.”

“The minority populations of the United States have been hardest hit. Many of them didn’t have the benefit of being able to work from home or work remotely. A lot of them were essential frontline workers … or individuals who lost jobs because jobs started to shut down.”

“Those individuals, if we start to say you can’t participate in society or in these different activities, we expect to see a widening gap … and a greater loss of public trust in minority populations who are already experiencing a significant amount of distrust with respect to social institutions and also public health institutions. We need to be able to continue to cultivate trust in individuals such that they’ll want to get vaccinated.”

“These are drugs that do not have full regulatory approval. That’s not a small point. These are drugs that have an emergency use authorization. So far, it seems like they have robust efficacy and it seems like they have robust safety. But we don’t know for sure yet.”

“Up until we have full regulatory approval for a drug, requiring people to take it – and that’s what a vaccine passport would do – it conditions participation on taking a drug that hasn’t received full regulatory approval. That essentially conscripts people to being research participants, which isn’t how we run clinical trials. It isn’t how we address the issue of informed consent in society.”

“I think it would erode public trust in the regulatory process.”


Lavanya Vasudevan

“Unless we can achieve widespread vaccinations and achieve herd immunity on a global scale, we are not going to be safe in the U.S. I think access is a big issue. According to UNICEF, over 130 countries have no access to the COVID-19 vaccine.”

“There are a lot of logistical and access-related challenges that play a role.”

Dr. Emmanuel Walter

“I do think access is going to be a big issue, probably more than hesitancy. There always will be vaccine-hesitant people but I worry about the access issue. One of our big drivers here in the United States … is the emergence of viral variants. If we don’t get a handle on that globally we may see the emergence of more variants and some of them could be more resistant to coverage by our current vaccines.”

“I think we do need to really make an effort to attack this on a global scale.”


Nita Farahany

“I’ve been surprised that there have been uncomfortable bedfellows together in opposition to vaccine passports. On the one hand, you have a lot of people talking about the equity issue that arise from the use of vaccine passports. And that’s an issue that’s a moment in time. If you’re talking about the U.S. … at some point there will be widespread availability of the vaccines such that anybody that wants to have the vaccine can have it, and they’ll have full regulatory approval. At that moment in time, some of the equity issues will no longer exist.”

“In some places there are strong libertarian and conservative voices joining and arguing there’s a liberty interest in not being required to have vaccinations. We have in the past and in certain contexts, whether it’s in health care settings or in education … required vaccinations, and it’s permissible. The mechanism by which this type of vaccine passport is rolling out is very different. We need to have a moment where we actually reflect on that and decide what the best pathway forward is.”

“Suddenly you have a lot of corporations trying to get into the game of owning different biometric information about individuals that would serve as a gateway to access and entry to different settings.”

“There is a political strain starting to emerge around a liberty interest; there’s this other strain really around equity and public trust. They all share in common an opposition. My hope is it won’t become a conservative versus liberal; instead people see there’s lot of commonality to the concerns. We need to look at the risks … and figure out what the right approach is.”


Dr. Emmanuel Walter

“Most of the information we have to date in terms of school attendance suggests it is OK for children to attend school if certain precautions are in place with social distancing and masking. I think in communities where that’s been done, it’s been done fairly successfully to date.”

“I do think the UK variant is a little bit different. We don’t have as much experience here in this country with that at this point. I don’t know we know for sure that should change, at this point, our recommendations for school attendance.”

“It’s really important for children’s wellbeing to attend school … for children and for parents. I don’t think we need to rush to change things without more information at this point.”


Nita Farahany

“The drugs included on those lists required for international travel have widespread availability for anybody who needs them; have full regulatory approval; are used in very limited context; are not governed by third-party corporations.”

“I worry that the use in a much broader context to participate in any aspect of society creates all of the other concerns – equity, distribution concerns, issues that we don’t have full regulatory approval, privacy concerns, etc.”

“It’s not that we cannot require vaccination in certain context; we do and we can. It’s a question of whether or not these passports are appropriate to be used by society across the board.”


Lavanya Vasudevan

“The messaging strategies that have been successful have been very tailored to (underserved) communities. Really, the use of tailored strategies is what’s been important.”

“Access is still a major issue for those communities. It’s very important to bring vaccines to those communities. Make sure they have access. Many are health care deserts, don’t even have pharmacies in some cases. So we really need to think about how to bring vaccines there.”


Nita Farahany

“They’re all relatively introduced in a voluntary sense. You don’t have to go to a restaurant. You don’t have to work. You don’t have to go to school. That’s sort of how people frame the voluntary-ness argument. But it’s not really voluntary. If people who accept the passport condition your participation on you having the passport … it is not voluntary in the sense of what we think of as a truly free and autonomous choice.”


Dr. Emmanuel Walter

“There’s really very few absolute contra-indications to getting a vaccine. You have to be of the right age for which it’s indicated. The only medical contra-indication is if there’s an allergy to the vaccine. Unlike some other vaccines, for example live virus examples, these vaccines really are pretty available for use in most of the population.”


Lavanya Vasudevan

“It’s something we need to keep in mind. The fact that there has to be a new vaccine developed each year … and the efficacy of the vaccine may vary. That by itself is a big reason why people choose not to get the vaccine. And there are all these myths about how you get the flu from the flu vaccine. We are hearing similar stories about COVID-19.”

“I think it’s not something we should take for granted now that we are reopening businesses and schools. We aren’t as isolated as we were last fall. There’s a really good chance the flu makes a comeback.”

Faculty Participants

Nita Farahany
Nita Farahany is a professor of law and a professor of philosophy at Duke and founding director of Duke Science & Society. Farahany studies the ethical, legal and social implications of emerging technologies.

Lavanya Vasudevan
Lavanya Vasudevan is an assistant professor in the Department of Family Medicine and Community Health and the Global Health Institute at Duke. She is also a faculty affiliate at Duke’s Center for Health Policy and Inequalities Research.

Dr. Emmanuel Walter Jr.
Dr. Emmanuel "Chip" Walter Jr. is chief medical officer of the Duke Human Vaccine Institute, where he directs the Duke Vaccine and Trials Unit. Walter is also a professor of pediatrics at Duke University School of Medicine. 

Duke experts on a variety of other topics related the coronavirus pandemic can be found here.