- Study shows dramatic decline in effectiveness of COVID-19 vaccines over time. Among veterans 65 and older who were inoculated with the Moderna vaccine, those who developed a “breakthrough” infection were 76% less likely to die of COVID-19 compared with unvaccinated veterans of the same age. https://www.seattletimes.com/nation-world/study-shows-dramatic-decline-in-effectiveness-of-covid-19-vaccines-over-time/ 24 comments science