RELATED: If You’re Fully Vaccinated, These Are the 5 COVID Symptoms to Look Out For. The study, which was presented at the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) this year, found that residents of care homes have a higher risk of experiencing breakthrough COVID infections. The researchers from Colmar analyzed a COVID outbreak that occurred at a care home in eastern France a month after a campaign to vaccinate its 93 residents and 73 staff members with Pfizer had ended. According to the study, 75 percent of the residents and 52 percent of the staff were fully vaccinated by mid-February. However, the outbreak started on March 15, and 26 percent of the residents and 22 percent of the staff became infected with COVID over the course of seven weeks. Half of the infected residents were fully vaccinated, with an average age of 91.ae0fcc31ae342fd3a1346ebb1f342fcb The researchers concluded that the efficacy of Pfizer’s vaccine against infection for elderly residents in care homes was reduced to 68 percent. This a significant drop from the general 95 percent efficacy against infection the CDC has reported for Pfizer, based on evidence from clinical trials in people 16 years and older. RELATED: For more up-to-date information, sign up for our daily newsletter. Unvaccinated residents in the care home were still three times more likely to develop COVID compared to those fully vaccinated. Infections among the vaccinated residents also appeared to be milder, as no severe cases were reported. Meanwhile, there were three severe COVID cases among the unvaccinated residents. “This outbreak highlights [the] need for high rates of vaccination of residents and healthcare workers in long-term care facilities and other centers accepting elderly patients and those with multiple underlying health condition,” Martin Martinot, lead researcher for the study and an internal medicine specialist at the Hopitaux Civils de Colmar, said in a statement. Martinot said that immunosenescence, which is the age-related weakening of the immune system, may contribute to the older adults still being at risk for COVID, even after vaccination. “Immunization against COVID-19, although very protective… seems a bit less effective in our oldest patients. Thus, achieving the highest rate of vaccination is important to prevent outbreaks and protect residents and healthcare workers,” he said. RELATED: Vaccinated People Who Get COVID Have These 3 Things in Common, Study Shows.