Impact of vaccinations and infectious diseases on the risk of melanoma--evaluation of an EORTC case-control study.

A significant correlation between a reduced risk of melanoma and BCG and vaccinia vaccination in early childhood or infectious diseases later in life has already been reported from the FEBrile Infections and Melanoma (FEBIM) multicentre case-control study. This correlation is further evaluated in this study based on 603 incident cases of malignant melanoma and 627 population controls in six European countries and Israel by means of a joint analysis of the influence of vaccinations and infectious diseases. In addition, the previously unconsidered impact of influenza vaccinations is evaluated for the whole study population. The strong effects of the frequently given BCG and vaccinia vaccinations in early childhood, as well as of uncommon previous severe infectious diseases, were apparently not cumulative. With the Odds Ratio (OR) being set at 1 in the absence of vaccinations and infectious diseases, the OR dropped to 0.37 (95% Confidence Interval (CI): 0.10-1.42) when subjects had experienced one or more severe infectious diseases, associated with a fever of > 38.5 degrees C, and had not been vaccinated with BCG or vaccinia. The OR was 0.29 (CI: 0.15-0.57) in those who had had a severe infectious disease and were vaccinated with either BCG or vaccinia and 0.33 (CI: 0.17-0.65) for those with 1 or more severe infectious diseases and who had received both vaccinations. We conclude that both vaccinations as well as previous episodes of having a severe infectious disease induced the same protective mechanism with regards to the risk of melanoma. Because of a 'masking effect' by the vaccinia vaccination, the protective effect of the BCG vaccination and of certain infectious diseases against cancer has remained undetected. The vaccinations contributed more to the protection of the population than a previous episode of having an infectious disease. In view of the termination of vaccinations with vaccinia in all countries and of BCG in many of them, these findings call for a re-evaluation of vaccination strategies.