Adult antibody thresholds are currently used to determine whether immunocompromised children should get a measles, mumps, and rubella (MMR) booster shot. However, a new study shows that these thresholds fail to identify a significant percentage of children who need to be revaccinated.

These findings, published in Clinical Chemistry, could help to ensure that immunocompromised children are protected from these viruses—which is especially important now that measles in particular could be experiencing a revival.

The U.S. declared measles to be eradicated in the early 2000s, but cases have been on the rise in the last several years, and the country is currently experiencing one of its worst outbreaks since the turn of the century.

Falling vaccination rates—fueled by the growing vaccine-skepticism movement—are to blame, as this has led to pockets of the country losing their herd immunity. And it isn’t just unvaccinated people who are at risk, as vaccines tend to be less effective in immunocompromised people.

Normally, this patient population is protected by herd immunity, but as herd immunity to measles wanes, it’s more important than ever for immunocompromised people to know whether they have vaccine-induced immune protection so that they can get a booster shot if not.

Measuring a person’s antibody levels is the standard method for determining whether someone has vaccine-induced immunity. However, the antibody levels that are considered adequate are based on thresholds derived from studies in adults, and age-appropriate thresholds for children have not been established.

In order to improve assessment of immunity in children, a team of researchers led by Dr. Sarah Wheeler of the University of Pittsburgh Medical Center set out to investigate whether there were age-specific differences in vaccine-induced antibodies in children aged 1 to 18.

The researchers gathered 472 blood samples from a healthy pediatric group with no history of chronic diseases that could affect immune response to vaccination. They also collected 114 samples from a pediatric group with autoimmune diseases, which can lead to inadequate vaccine response.

The researchers then measured the levels of MMR, hepatitis B, and varicella antibodies in the samples and compared the results with adult antibody levels.

From this, Wheeler’s team found that, at every measured timepoint, both pediatric groups had higher antibody thresholds for measles, mumps, and rubella than adults.

This means that nearly 25% of all children in the study would have been inaccurately classified as having an adequate vaccine response if they had been assessed using adult antibody thresholds alone. Altogether, these findings show that age-appropriate antibody thresholds need to be used when determining immunity to MMR in the pediatric population.

“This will further improve our ability to evaluate and provide needed immunity against vaccine-preventable diseases in children at risk due to endogenous or exogenous immunosuppression,” Wheeler said. “Future work in this area could also investigate age-appropriate cutoffs for other common vaccinations.”

Provided by
Association for Diagnostic and Laboratory Medicine (ADLM (formerly AACC))