These factors "have been key in improving overall outcome," Pinato said. 'Glimpse of hope' when drugs limit vaccine antibodies People taking a class of drugs known to limit the antibody response of the mRNA COVID-19 vaccines from Pfizer /BioNTech or Moderna may get some protection from another part of the immune system, according to a small study published in Clinical Infectious Diseases https://academic.oup.com/cid/advance-article/doi/10.1093/cid/ciab954/6430423.