An interval of over 10 weeks between COVID-19 vaccine doses was associated with SARS-CoV-2 antibody levels up to 11 times higher than with an interval of 2 to 4 weeks in never-infected participants, according to a preprint paper to be presented at the upcoming annual congress of the European Society of Clinical Microbiology & Infectious Diseases (ESCMID).The meeting starts tomorrow in Lisbon, Portugal.Researchers from the UK Health Security Agency (HSA) measured antibody levels in blood samples from nearly 6,000 healthcare workers who received two doses of the Pfizer/BioNTech COVID-19 vaccine.
Participants were enrolled in the UK's SARS-CoV-2 Infection and Reinfection and EvaluatioN (SIREN) study, according to an ESCMID press release issued yesterday.Of the 5,871 participants, 3,989 received their first vaccine dose at least 21 days earlier, and 1,882 received their second dose at least 14 days before.
Some vaccinees had previously tested positive for COVID-19.Women, ethnic minorities had strongest responseOver 99% of never-infected participants had detectable antibodies after vaccination.
After the first dose, previously infected participants' antibody levels were up to 10 times higher than those of their COVID-naïve counterparts.