gms | German Medical Science

Risk factors for most childhood cancers are largely unknown but there are suggested factors that act via immunological pathways. In this context, immunizations are discussed as protective factors. However, findings of previous observational studies investigating the association between immunizations and childhood cancer are inconsistent.

The PRECHIC project analyses a cohort of more than 1.8 million children born between 2004 and 2019 in Germany to examine vaccination prevalence, incidence of cancer and impact of immunization on the risk of childhood cancer. This cohort is selected from the German Pharmacoepidemiological Research Database (GePaRD), a claims database covering about 20% of the German population. Additionally to sociodemographic characteristics, it contains information on vaccination and drug dispensations as well as on diagnoses, procedures or services coded in the inpatient or outpatient setting. These codes will be used to assess the presence of potential risk factors of childhood cancer, like birth conditions, inherited disorders, atopy, autoimmune diseases, infections, medications, medical examinations and therapies. Moreover, for about 80% of newborns the claims data of their mothers will be linked to assess medical risk factors during fetal life such as the immunizations of the mother. This cohort is followed up from pregnancy or birth to death, end of continuous insurance or end of observation period (December 31st, 2022), whichever occurs first. The maximum follow-up period is 18 years resulting in about 15.5 million person-years under risk and about 2,500 cases of childhood cancer.

A specific strength of the PRECHIC project is the absence of non-responder bias and recall bias since, e.g. the immunization status does not rely on self-reports. Another strength is the availability of maternal information regarding medical risk factors during fetal life. The analyses will be conducted following the principle of target trial emulation, which avoids design-induced biases. The large size of this historical birth cohort facilitates precise effect estimates and thus provides a promising approach to investigate the impact of immunization on childhood cancer. In the long term, it may be used to investigate further potential risk factors for childhood cancer.

The authors declare that they have no competing interests.

The authors declare that an ethics committee vote is not required.

The contribution has already been published: Der Abstract wurde als Poster-Präsentation beim diesjährigen World Congress of Epidemiology (24.-27. September 2024) angenommen.