Another severe and often fatal complication for children under 2 years old is the development of subacute sclerosing panencephalitis, which can happen 7-10 years later.

2岁以下儿童中，另一严重且常致命的并发症是亚急性硬化性全脑炎（SSPE）；这种病可在发病后的7-10年发生。