Year: 2009
Type: dissertation
Study design: Observational Study
Abstract: Viral childhood diseases have been implicated in the pathogenesis of multiple sclerosis (MS).\nSwedish mass vaccination programmes resulted in radical changes in the panorama of the\ntargeted infections. Vaccines against measles, mumps and rubella were implemented in the\nearly 1970s. In 1982, Sweden introduced the two-dose measles-mumps-rubella (MMR)\nvaccine, as the first country in the world. Measles sharply declined in the 1970s. In cohorts\nborn since 1981, measles, mumps and rubella were virtually eliminated. The main aim of this\nthesis was to investigate whether specific viral childhood diseases, or the vaccinations against\nthem, influence the risk of developing MS. This was accomplished by a study of MS incidence\nin vaccinated cohorts, by a case-control study and – indirectly – by a study of birth order in\nsibships.\nThese studies were based on unique underlying conditions. Individual data on infections and\nvaccinations were documented in child health and school health records. The proportion of\nindividuals with a history of vaccination-targeted infections was suitable for statistical\nanalyses. Furthermore, there was a long tradition of MS incidence studies in Gothenburg. We\nupdated the Gothenburg MS registry obtaining a study material of 534 incident MS patients\nborn from 1959 to 1990. The incidence of MS was analysed in four population cohorts, each\nselected to represent a new vaccination programme. Questionnaires on measles, mumps,\nrubella, or the vaccinations, and two other infections, varicella and infectious mononucleosis\nwere completed by 509 MS patients and 2067 controls, born 1959 to 1986. Data on infections\nand vaccinations were obtained from the questionnaires and, for a selection of 206 MS patients\nand 888 controls, also from child health and school health records.\nWe found no major influence of birth order on MS risk. The observed number of first-born\npatients did not significantly differ from the expected number, and the proportion of first-borns\ndid not differ from that in a control cohort born during the same period. We found no\nsignificant change in the incidence of MS in any of the four population cohorts defined by mass\nvaccinations. The long-term MS incidence showed a significant gradual age-dependent\nincrease, which was unrelated to the introduction of the vaccination programmes. MS patients\nand controls reported similar frequencies of measles, mumps, rubella and varicella. The results\nfrom the child health and school health records confirmed the results from the questionnaires.\nInfectious mononucleosis was associated with 2-fold higher MS risk. In the light of this\npositive finding, the negative findings for the other studied infections are more convincing.\nSimply being vaccinated against measles, mumps or rubella did not change the risk of MS.\nSimilarly, MMR vaccinated individuals were not at higher or lower MS risk than MMR\nunvaccinated individuals. Among MMR vaccinated individuals, the MS risk was increased in\nthose vaccinated before age 10 only. Those vaccinated both before and after age 10 had\nintermediate MS risk.\nThe specific viral childhood diseases measles, mumps, rubella and varicella do not influence\nthe risk of MS, and may be dismissed as risk factors for MS. Infectious mononucleosis is a\nmoderate risk factor for MS. Vaccination against Epstein-Barr virus infection should be\nconsidered. The risk of MS in MMR vaccinated does not differ from that in MMR\nunvaccinated individuals. The finding that MMR vaccination at a low age only may be related\nto MS risk needs to be confirmed in other study material.
Author: Cecilia Ahlgren
Language: English
Subfield: Clinical Neurology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W628434278