Immunity to diphtheria among children in Northern Norway and North-Western Russia

In 1990, diphtheria re-emerged in Russia and during the following four-year period the resulting epidemic reached all the Newly Independent States (NIS) of the former Soviet Union. Several neighbouring countries of NIS, Norway included, have experienced sporadic imported cases. A sero-epidemiological study among children in Northern Norway and North-Western Russia was performed in order to evaluate protection against diphtheria and how differences in vaccination programmes affect immunity. A total of 664 sera, 400 from Norwegian and 264 from Russian children, were examined for antibodies against diphtheria, using an in vitro toxin neutralisation method. The Russian children studied had satisfactory protection in all age groups examined. The Norwegian children had poor protection against diphtheria from the age of 7 years until they received the booster dose at the age of 11. Therefore, a revision of the Norwegian vaccination programme, including a booster dose at school-entry age, seems warranted.