A study conducted in four Nordic countries found that receipt of the measles, mumps, and rubella (MMR) vaccine was associated with an 11% reduced rate of antibiotic use in children under 2, researchers reported yesterday in the journal Vaccine.
Using national registries, Nordic researchers analyzed a cohort of 831,287 children under the age of 2 years in Denmark, Finland, Norway, and Sweden who had received a third dose of the diptheria-tetanus-acellular pertussis vaccine (DTaP) but had not yet received the MMR vaccine. They then investigated whether receipt of the MMR vaccine after a third DTaP dose was associated with reduced rates of antibiotic use compared with three DTaP doses.
The proportion of children in the study who had received a recorded dose of MMR vaccine before age 2 ranged from 78.6% in Finland to 96.2% in Norway. In all countries, receipt of MMR vaccine after the third DTaP dose was associated with reduced rates of antibiotic treatment, with an adjusted hazard ratio (aHR) of 0.92 (95% confidence interval [CI], 0.91 to 0.93) in Denmark, 0.92 (95% CI, 0.90 to 0.94) in Finland, 0.84 (95% CI, 0.82 to 0.85) in Norway, and 0.87 (95% CI, 0.85 to 0.90) in Sweden. The overall aHR for all countries was 0.89 (95% CI, 0.85 to 0.83). The results were similar for boys and girls.
Bias may explain some of the association
But the researchers also observed a lower rate of antibiotic treatments among children who had received three DTaP doses compared with two, with reductions ranging from 14% in Denmark to 29% in Sweden. The findings of this negative control analysis, they say, suggests the lower rate of antibiotic treatment associated with receipt of MMR vaccine is affected by residual confounding.
"The magnitude of the association in the negative control analysis does indicate that bias related to receiving vaccines according to recommendation may at least partly account for the observed beneficial association of MMR vaccination," the study authors wrote.