New UW Research Shows Power of COVID-19 Vaccine
Study shows vaccine reduced spread of virus among person's close contacts.
COVID-19 vaccine. (Pixabay License).
According to state immunization data, the number of people in Wisconsin who received a COVID-19 vaccine in September is down about 33 percent compared to last year.
Researchers have long known from clinical trials that the COVID-19 vaccine protects individuals against severe illness. But they did not know whether the vaccine also reduces the spread of the disease. Until now.
In a forthcoming study, a University of Wisconsin-Madison economist analyzed data from the pandemic and found real-world evidence that the COVID-19 vaccine actually reduces the spread of the disease between vaccinated people and their close contacts.
Dan Sacks is an associate professor of risk management and insurance in the Wisconsin School of Business. He researches the economics of health.
In the study, Sacks found that among children in Indiana, the COVID-19 vaccine reduced the number of infections by 80 percent for those who received it. Even more significantly, he found, every two vaccinated children prevented approximately one additional COVID-19 case in their households.
Sacks’ findings will be published in the American Economic Journal in January.
He joined WPR’s “Wisconsin Today” to explain his research on the COVID-19 vaccine and how people can use it to inform their own health decisions this season.
This interview has been edited for brevity and clarity.
Kate Archer Kent: What stands out to you in the research about the indirect effects of the COVID-19 vaccine?
Dan Sacks: We started by looking at what happens in a household when kids get vaccinated. The reason we’re looking at the kids is that they were the last to be eligible for the vaccines in Indiana. We could compare what happens to families with kids who became eligible because of their age, versus families with just younger kids who weren’t yet eligible.
We find pretty substantial protective effects for families. So if a kid in the family is vaccinated, that protects the kid, and for every child case of COVID you prevent, that prevents about half a case of COVID in the rest of the family. … It probably won’t surprise you that for the families that vaccinate their kids, mostly the parents are already vaccinated. So we’re finding fewer breakthrough infections for family members who are themselves already vaccinated.
KAK: You’ve been talking about households — what do we know about the protection the vaccine offers at school?
DS: I have two young kids at home and they sneeze all over me. It’s no surprise that their vaccines protect me. But we also wondered about less close contacts, people that you don’t interact with face to face super often.
We wanted to see if there was some protective effect of having more vaccinated kids in your school. We found that, no, we didn’t really see any protective effect. That was a bit surprising to us. Maybe there’s a small effect that we’re not able to pick up. Maybe there’s no effect. That’s certainly possible, especially because there were a lot of COVID mitigation measures in place.
Another possibility: We’re measuring what is sometimes called herd immunity, or how much protection we get collectively when more people are vaccinated or otherwise have immunity. … Schools in Indiana did not have very high vaccination rates. So it’s possible there just wasn’t enough vaccination going around.
KAK: Do you have evidence from your research that might affect people’s behavior toward getting a COVID booster this fall or winter?
DS: I think that many people experience short, but real, side effects of getting it. So I think that there’s some reason not to want to vaccinate. But I think most people also recognize that there’s a health benefit of getting a COVID vaccine or COVID booster, which is that it’s a nasty illness and you don’t want to experience that.
What our research adds is two things: I think some people are not sure how much the COVID vaccines work in the real world outside of the clinical setting. We found that they were very effective for the kids who got them.
The second is that a lot of the current guidance around the COVID boosters focuses on personal risks and personal decisions. That’s an appropriate framework. But one thing that it misses is that you might want to get vaccinated not just to protect yourself, but to protect your family and people that you interact with closely. We have some evidence that, in the past, that was a real effect of COVID vaccines.
KAK: Based on all of this research that you have done on the direct and indirect effects of the COVID-19 vaccine, what policy decisions could come out of this?
DS: We ended up finding the clearest effects in fairly narrow areas, like households. That’s what we know for sure. I suspect that something similar happens among coworkers who work closely together. What that tells me is that there’s a pretty strong case for groups of people who interact closely together to decide it’s important that they all vaccinate.
In the past, especially at the tail end of the pandemic, some states started proposing laws to make it illegal for an employer to require vaccination. Our results say that those laws would have real costs if you wanted to promote the health of your employees, particularly if they wanted it by requiring them all to vaccinate. Bans on employer vaccine mandates undermine that.
Wisconsin researcher finds COVID-19 vaccine offers stronger protection than once thought was originally published by Wisconsin Public Radio.
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