With the measles outbreak in Wisconsin at 144 cases as of Sept. 8, state public health officials are urging people to get vaccinated. Of all the confirmed cases statewide, all but one of those sickened are unvaccinated and four of the cases led to hospitalization.
"I think it's pretty clear that we're not getting the best guidance from the federal government right now about the safety of vaccines," says Dr. Freddy Caldera, a professor of medicine at the UW School of Medicine and Public Health. "We know prior to the pandemic, greater than 95% of kids going into kindergarten were vaccinated. But as you kind of break some public trust for something that physicians and other providers never saw... you can create a little doubt. We want to build back some of that trust with patients so that they know the vaccine is safe."
Caldera is also a gastroenterologist who's written about the importance of community immunity and how immunocompromised people with inflammatory bowel disease (IBD), organ transplants and other conditions navigate concerns about their risk during outbreaks.
New research shows that a commonly used measles antibody test may incorrectly suggest that previously vaccinated adults with IBD are not protected against the disease. Caldera wants to reassure patients that this is not the case and they are most likely protected.
"I've been doing vaccine research at UW now for almost 10 years because I take care of patients with IBD who are on these biologic medicines and they get very concerned. So when the Texas [measles] outbreak started last year, I had a lot of my colleagues reach out to me and say, what should we be doing?" he recalls.
"We had had some previous studies looking at how well the measles blood test worked, but measles was gone. So I didn't think we needed to work on it. So we started to work because we didn’t want someone who’s immunocompromised then call their doctor or their provider to say, 'Hey am I protected?' and now started changing their behavior because a blood test was not accurate."
By taking blood from vaccinated patients who had been in previous studies, the research team used a regular blood test commonly found at a lab or hospital and compared it to a more sensitive blood test. "We found that the more sensitive blood test we did in the lab actually was more accurate and some of the tests in the clinic or hospital lab were actually false negative," notes Caldera. "You could say, well, why would a hospital have a false negative test? Because this test was developed to look for an infection, not to look at what happens after you get vaccinated. Because after you get vaccinated, the blood antibody level is lower typically. It doesn't mean you're not protected, it's just lower."
If you aren't sure you are vaccinated against the measles, Caldera points to the statewide registry where you can look up your immunization records. If you were born before 1957, you can be considered immune because you lived through a time when the virus was widespread and almost certainly contracted the disease as a child.
"For patients, I would just remind them that this is a very effective vaccine. That they shouldn't rely on getting a blood test because that blood test is not great and it may change their behavior because regretfully we're going to continue to see these measles outbreaks occur across the country. And hopefully we can contain the one in Wisconsin," he adds.
