Complex sentence: Between 2000 and 2006, several hundred children in Finland had serious adverse events from the vaccine, including osteitis and osteomyelitis, disseminated (usually fatal) BCG infection, arthritis, and lymph node abscesses.
Split into simpler sentences: Between 2000 and 2006, several hundred children in Finland had serious adverse events from the vaccine. Adverse events included osteitis and osteomyelitis, disseminated (usually fatal) BCG infection, arthritis and lymph node abscesses.