Study Finds Vaccines Don’t Weaken Babies’ Immune Systems

In response to concerns from parents about whether multiple vaccines in early childhood could weaken their children’s immune system, researchers conducted a study that examined whether the vaccine schedule was associated with an increased risk of infections not targeted by vaccines (referred to as “nontargeted infections”). They found no statistically significant differences in estimated cumulative vaccine antigen exposure through the first 23 months of life.

The nested case-control study examined 193 children with nonvaccine-targeted infections and 751 controls without nonvaccine-targeted infections in six U.S. healthcare organizations participating in the Vaccine Safety Datalink. Participants were children ages 24 months through 47 months born between Jan. 1, 2003, and Sept. 31, 2013, who were followed until Dec. 31, 2015. Cases of nonvaccine-targeted infection were matched to controls by age, sex, healthcare organization site and chronic disease status. Cumulative vaccine antigen exposure was estimated by adding the number of antigens in each vaccine dose received from birth through age 23 months.

Among the 944 participants (mean age 32.5 months; 45 percent female), the estimated mean cumulative vaccine antigen exposure was 240.6 for cases and 242.9 for controls, with a between-group difference for estimated cumulative antigen exposure -2.3. The researchers concluded that “among children from 24 through 47 months of age with emergency department and inpatient visits for infectious disease not targeted by vaccines, compared with children without such visits, there was no significant difference in estimated cumulative vaccine antigen exposure through the first 23 months of life.”