Outbreaks in the 21st century include more than 300,000 cases in China in 2013 and more than 56,000 cases in England and Wales in 2004–2005. In the latter outbreak, most cases were reported in 15–24 year olds who were attending colleges and universities. This age group was thought to be vulnerable to infection because of the MMR vaccine controversies when they should have been vaccinated or MMR vaccine shortages that had also occurred at that time. Similar outbreaks in densely crowded environments have frequently occurred in many other countries, including the U.S., the Netherlands, Sweden, and Belgium.
oUTbReakS in thE 21st centUry include MOre THAn 300,000 caSes in ChiNA IN 2013 and MoRe Than 56,000 caSes iN eNGlAnD AnD waLEs iN 2004–2005. IN the lAtter oUtBrEAk, most cAses WeRe rePORTed iN 15–24 year olds wHo werE atTEnDinG colLegEs And univERsitIEs. this age GRoup was ThoUGhT to be vulnErabLe tO inFectiON BEcause of thE MMR vaccine COnTrOVeRSieS wheN they Should hAvE bEEn vACcinATeD or MmR vAccinE Shortages THat haD aLso OccurreD at tHAt Time. siMilaR oUTbReAks iN dEnsElY cROWdEd environments have FreqUENtLy OcCurred iN manY otHeR CounTriEs, includINg the u.s., thE nEtHerlaNDs, sweden, And BelgiUM.