In a longitudinal study we examined the impact of age on negative emotional reactions, compliance with health guidelines and knowledge about the virus during the COVID-19 epidemic. A total of 2509 people participated in a two-phase study: 1424 participants in the first phase (March 12-21) and 1085 participants in the second phase (April 23 to May 5). Age was categorized into 4 groups: age 18 to 30, age 31 to 40, age 41 to 50, and age 51 and over. In the first and second phase, compliance with health guidelines was highest among participants over the age of 50. Knowledge was significantly higher in the second phase than in the first among participants over age 50 and those between the ages of 40 and 50. In the second phase, knowledge did not differ by age group. Negative emotional reactions were significantly higher in the first phase than in the second. Moreover, negative emotional reactions were higher among participants up to age 30 than among all other participants. Perceived susceptibility did not differ by phase or by age group. The paper underscores the impact of age during the COVID-19 epidemic and points to the necessity of taking the needs of different age groups into consideration.