There is some evidence that one dose of two-dose vaccines (Pfizer-BioNTech, Moderna) can provide some protection against COVID-19 and is therefore better than not getting vaccinated at all. However, two doses of two-dose vaccines, given at the proper intervals, is still the U.S. recommendation. At this time, the CDC is also recommending a third shot for individuals with weak immune systems. Stanford Health Care will continue to follow CDC guidance for populations who may receive the booster dose. Please continue to check this website for updates. Please remember that vaccines are just one of several tools to help end the pandemic. It is essential for everyone, including those who have been vaccinated, to continue using all the tools available to help stop the spread of infection, including covering mouth and nose with a mask, washing hands often, staying at least 6 feet away from others, testing when indicated, and following all guidance from state and county health officials.