Autoimmune reactions to vaccinations have been reported since vaccines were introduced into modern medical technology. Here, we discuss the possible underlying mechanisms of autoimmune reactions following vaccinations and review cases of autoimmune diseases that have been correlated with vaccination. Molecular mimicry and bystander activation are reported as possible mechanisms by which vaccines can cause autoimmune reactions. Idiopathic Thrombocytopenia Purpura, Myopericarditis, Primary Ovarian Failure, Systemic Lupus Erythematosus (SLE) and Acute Disseminated Encephalomyelitis (ADEM) are all autoimmune conditions with reported links to vaccinations. Genetic predisposition was a definite risk factor for people experiencing autoimmune conditions following immunization; thus understanding the genome of patients is vital for both the development of future generations of vaccines and personalized medicine. Further study is encouraged into the direct associations between vaccines and autoimmune conditions, and the biological mechanisms behind them.

Bordetella pertussis is the causative agent of pertussis, an infectious disease highly communicable, with a secondary attack rate up to 90% among non immune household contacts. In Brazil there are few studies identifying infant pertussis sources. The aim of this study was to demonstrate a possible source of infection of B. pertussis among household contacts with infants confirmed with pertussis by laboratory criteria, using Pulsed Field Gel Electrophoresis (PFGE) that allows the identification of strains which can be epidemiologically linked to them.

From November/2011 to May/2012, nasopharyngeal swabs were collected from infants (< 7 months) suspected of pertussis. A total of 97 index cases were confirmed pertussis by PCR and/or culture. Samples were collected from up to five household contacts of each index case totaling 353. The strains were subtyped by pulsed-field gel electrophoresis and serotyping.

A total of 97 index cases and theirs 28 household contacts had the pertussis diagnosis confirmed by culture and/or Real-Time PCR. Among them was possible to characterize five groups of index cases/household contacts linked according to the degree of relatedness and genetic profiles obtained by PFGE technique, indicating the parents as a probable source of transmission of the disease to infants. Accordingly to the serotypes, all the five groups presented an agreement among the results of the index cases and their household contacts.

Based on our available evidence, it can be assumed that parents were a possible source of infection for these infants under seven months of age.

Hence we suggest with this study that mothers and fathers still play an important role in transmitting this disease to unprotected infants and new strategies are necessary to prevent this important disease that represents a great threat to public health.