Winter is here and with the cold temperatures and the holidays come the seasonal epidemics of pneumococcus, a potentially deadly disease for the young and the elderly. And while the arrival of the disease is reliably predicted each passing year, the precise factors that affect its rapid transmission from person to person remain poorly understood. New research led by the Yale School of Public Health sheds light on what drives seasonal variations of the bacterial pathogen and provides information that may enhance the effectiveness of vaccine delivery. The results were published recently in the journal Clinical Infectious Diseases.