Getting childhood vaccinations according to the recommended schedule appears to reduce the risk of hospitalization for infections, according to the results of a Danish study.
Young children who received the measles, mumps, and rubella (MMR) vaccine on time were less likely to be hospitalized for infectious diseases than were those who did not get their shots in the recommended order, according to the results of a study published in the February 26, 2014, issue of the Journal of the American Medical Association
Drawing from previous research that has shown that live vaccines, such as MMR, may have nonspecific effects in low-income countries, such as reducing the rate of mortality for causes unrelated to the vaccine, the current study
set out to determine whether such an association existed in high-income countries as well. The researchers analyzed vaccination and hospital admissions data for children born in Denmark from 1997 through 2006, comparing hospitalization rates for children who were vaccinated with the MMR and the Haemophilus influenzae
type b (DTaP-IPV-Hib) vaccines according to schedule with those who did not receive the shots in the recommended order.
Infants were recommended to receive 3 doses of the DTaP-IPV-Hib vaccine at 3, 5, and 12 months of age, respectively, and the MMR vaccine at 15 months of age. Children who had received 2 doses of the DTaP-IPV-Hib vaccine before the age of 11 months were followed from the age of 11 months to 2 years and were separated into 2 groups: those who followed recommendations and received the third dose of the DTaP-IPV-Hib vaccine before the MMR and those who received the MMR before the third dose of DTaP-IPV-Hib.
A total of 495,987 children who had 56,889 hospitalizations for any type of infection were included in the study. The results indicated that children who received the MMR vaccine after the DTaP-IPV-Hib vaccine as recommended had significantly lower rates of hospital admissions than those who received the third dose of DTaP-IPV-Hib after the MMR. Children who received the vaccines out of order had a 5.1% chance of hospitalization for any infection between the ages of 16 and 24 months, compared with a 4.6% chance among those vaccinated according to recommendations. Among children who received the vaccines in the order recommended, the association was strongest for lower respiratory tract infections.
Although the study’s results suggest that the MMR vaccine has beneficial nonspecific effects, the authors of an accompanying editorial
note that bias is hard to control in observational studies such as this one.
“The possible implications of any such nonspecific vaccine effects for the infant immunization schedule remain unclear,” they write.
Although more research is needed to support the findings, the authors of the study note that even in high-income countries, timely vaccination is far from universal; only 50% of children included in the study were vaccinated according to the recommended schedule.
“Physicians should encourage parents to have children vaccinated on time with MMR and avoid giving vaccinations out of sequence,” they suggest.