Background: Immunizations are one of the most effective health initiatives of the twentieth century, but many people do not receive sufficient immunizations in several parts of the world. Every year, about three million people around the world die from diseases that can be prevented by vaccines; half of the dead were infants and children. However, community health care workers have become increasingly recognized and acknowledged as an important and efficient intervention essential for increasing community-centered health services, especially in deprived areas. Aims of the study: To evaluate the level of health care workers' knowledge about immunity and vaccination at primary health care centers. Methodology: A cross-sectional descriptive study design conducted for the periods 27 \ September \ 2020 to 25 \ April \ 2021, among (315) health care workers who are selected by non-probability sampling (convenience sample), self-administered questionnaire, the scores obtained for answers to closed-ended questions were used to determine the level of knowledge, reverse questions were used, several statistical measures were used by using Statistical Package of Social Sciences version 24, in order to analyze and evaluate the results of the study. Results: The findings showed that health care workers have a moderate level of knowledge about immunity and vaccination. Conclusion: There was a moderate level of knowledge about immunity and vaccination among health care workers. In addition, the greatest part of participants in this study is medical assistants and nurses. Recommendations: The researcher recommends implementing an educational program designed for health care workers about immunity and vaccination in all primary health care centers