[Measles immunity in the Swedish population]

Sweden eliminated measles in the 1980s through high vaccination coverage among children. Most adults born during the 1960s or earlier have immunity to measles following prior infection, while those born later mainly rely on vaccine-induced immunity. The latest serological study conducted in Sweden, with samples collected in 2016, showed an overall seroprevalence of 93 %. Persons born in 1982-1996, who were the first to receive two doses, had a lower seroprevalence of 83 %. This does not necessarily indicate waning protection, as cellular immunity also plays a role against disease. Furthermore, breakthrough infections remain rare. However, older vaccinated groups show higher rates of suspected breakthrough cases. Immigrants' immunity varies. Children arriving after six years of age often match Swedish-born peers, but adults from regions with weak vaccination programs (e g, former Yugoslavia, the Baltics, and Russia) may lack protection. A 2014-15 study from Skåne Region found that measles immunity among newly arrived adult migrants ranged from 44% to 97%, reflecting past infection or vaccination gaps. Continuous monitoring of immunity is crucial, as waning antibody levels and lack of natural boosting in the elimination settings could affect long-term immunity. The Public Health Agency of Sweden recommend adults to review their vaccination status, especially before travelling abroad, and some regions offer catch-up doses to adults free of charge to close immunity gaps.