People who have recovered from COVID-19 had a robust antibody response after the first mRNA vaccine dose, but little immune benefit after the second dose, according to new research from the Penn Institute of Immunology. The findings, published today in Science Immunology, suggest only a single vaccine dose may be needed to produce a sufficient antibody response. The team found that those who did not have COVID-19—called COVID naïve—did not have a full immune response until after receiving their second vaccine dose, reinforcing the importance of completing the two recommended doses for achieving strong levels of immunity.