A Duke expert answers new and lingering questions about coronavirus vaccines

Months after people first began receiving vaccines to protect them against the coronavirus, old questions persist — Do they work? Are they safe? — and new ones have appeared — Do I need a booster? Can I still get COVID?

The News & Observer spoke to Dr. Chip Walter, chief medical officer of the Duke Human Vaccine Institute and a professor of pediatrics at Duke, about why second doses are important, whether boosters are needed, and what to expect after being vaccinated. Here’s what he had to say:

If I’m fully vaccinated, can I still get COVID-19?

Walter: I think we all know that the vaccines aren’t 100% effective — they’re not perfect. So the answer is yes. I think you’re less likely to get COVID, but you still can get COVID after getting vaccinated.

You know, the vaccines aren’t 100% effective, but they’re pretty good. Depending on the vaccine, the ranges are high 60s to 95%. Some of those earlier vaccines with higher efficacy rates were assessed under optimal conditions without variance, so I think those were probably high-end estimates.

But the long and short answer is yes, you can get COVID after getting a vaccine.

If you do get COVID-19 after getting the vaccine, can you transmit it to other people?

Walter: I think the evidence is evolving, but certainly there are those people where you can detect virus after being vaccinated if you have a breakthrough case. And so I think the assumption would be that if you can detect the virus there, yes, you can potentially shed or transmit it to others.

What’s the rate of that? I don’t think we quite have that information yet. It’s probably less — you’re probably less likely to transmit it to others if you have been vaccinated, but I would not say there’s 100% assurity that you couldn’t give it to someone else.

Why is it so important to get the second dose for the two-dose vaccines from Pfizer and Moderna?

Walter: I think that data has been there for a while, and I think we know that after receiving the second dose, particularly with these mRNA vaccines, these people’s antibody responses were significantly higher than they were after the first dose and really were more equivalent to that of people who had recovered from infection.

So I think we kind of knew early on that people, at least in terms of their immune response, responded better after two doses of vaccines than after one dose of vaccine.

What is the purpose of a booster shot? Will you need one if you’re fully vaccinated?

Walter: I think we’re still trying to figure that out. Whether you need a booster shot or not — that information is quickly evolving, and I think we’ll probably have more in the next month or two.

Regarding that, it’s certainly a current area of study. If you look at, for example, other respiratory viruses like the flu, we know that after six months your immunity wanes. Also, the viruses really pretty much drifted from earlier in the season in many cases. So for those reasons, because immunity wanes and the virus drifts, we recommend that people get [the flu vaccine] on a yearly basis.

I think the evidence from the six-month information that I’ve seen earlier showed that the immunity was still pretty good. But we know that certainly there do seem to be breakthrough cases occurring. The data in Israel actually suggested that [immunity] dropped over time, so I think there’s this fear that we potentially may need booster vaccines.

I’m not going to say for sure we’re going to need them, but I think there are hints that we likely will need a booster. I think the exact timing of that is still to be determined at this point, but I think the evidence suggests that we may need that.

Are the current vaccines effective against different coronavirus variants?

Walter: Most of them look pretty effective against the variants. There’s some data for some of the vaccines that they may not be, but the mRNA vaccines — like Moderna and Pfizer — look pretty good against the variants at this point.

That doesn’t suggest that there may be new variants that start to occur or that crop up that the vaccines may not cover. And that’s really why I think we’ve made the case that we need to get as many people immunized as possible, so we don’t keep spreading the virus and potentially developing more variants. I think that we really just need to get way more widespread vaccination coverage.

Is it still beneficial to wear a mask if you’re fully vaccinated?

Walter: This is evolving as well. I think if you’ve been vaccinated, you clearly should be protected against getting a severe COVID illness, being hospitalized and potentially death.

Now, it’s not 100%, but you should be pretty well protected. The data suggest that people that are getting hospitalized due to COVID right now are people who have not been vaccinated, so I think vaccination prevents that.

That said, it doesn’t necessarily keep you from getting COVID, probably. I think we know that masks work. If you don’t want to get even a minor illness from COVID or potentially spread it, wearing masks in that case may be good. Clearly, if you haven’t been vaccinated, you should still be wearing a mask.

I think the issue comes up for young children, particularly as they go back to school: Should they be wearing masks? Most of them can’t be vaccinated at this point, so clearly they should be wearing masks.

I think it then becomes a personal preference at this point. If you’re in an area where there’s a lot of infection occurring and low vaccination rates, then I think wearing a mask, particularly if you’re indoors and a congregate setting, makes sense. So if you ask me, if I’m in a close- quartered area, going into a store or something with a lot of people, then I think a mask is still reasonable.