In early childhood, immunization with the DTP vaccine can contribute to the development of bronchial asthma due to the direct activation of Th-2 lymphocytes or an indirect decrease in microbial load, which disturbs the balance between the Th-1 and Th-2 immune response. This hypothesis is supported by the fact that an IgE-mediated allergic reaction to antigens introduced during vaccination most often occurs in children immunized with the DTP vaccine, and is particularly pronounced in people with atopy.

The epidemiological data on the relationship between vaccination with the DTP vaccine and the risk of developing bronchial asthma are contradictory. Some studies show an increased or decreased risk of developing asthma, while others show no pattern.

The purpose of the retrospective cohort study was to determine the effect of timing of vaccination with a whole cell DTP vaccine for children under 7 years of age on the risk of developing bronchial asthma at the age of 7 years..

Researchers analyzed vaccination and health status data from a group of children (n = 11,531) who received at least 4 doses of the DTP vaccine before the age of 7 years.

Bronchial asthma was diagnosed in 11.7% of those examined. Among them, boys predominated (3: 2). 70.3% lived in large cities, 25% came from low-income families and 10.1% of mothers suffered from bronchial asthma.

As a result of the study, it was found that in children who received the first dose of DTP vaccine after 2 months after the recommended immunization period, the risk of bronchial asthma was reduced by 2-fold and the incidence was 5.9%. The researchers note that with the delayed administration of three doses of the DTP vaccine, the probability of developing bronchial asthma is reduced by 60%. However, delayed administration of the second and third doses of the vaccine with the timely receipt of the first does not affect the incidence of bronchial asthma.

The authors emphasize the need for further research to better understand the relationship between vaccination and the development of an allergic disease, as the notion that vaccination is harmful can undermine the effectiveness of population vaccination programs.