COVID Vaccination (IMAGE) University of California - San Diego Caption Waning effectiveness over time, combined with the more contagious delta variant and the end of masking mandates, have boosted cases of COVID-19 among fully vaccinated health workers. Credit UC San Diego Health Sciences Usage Restrictions Use photo credit License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.