sentence1: Last year, there were shortages of shots for diphtheria-tetanus-whooping cough, measles-mumps-rubella, pneumococcal disease, tetanus and chicken pox nationally.
sentence2: In the past two years scientists say there have been vaccine shortages for diphtheria-tetanus-whooping cough, measles-mumps-rubella, pneumococcal disease, tetanus and chicken pox.