15-month follow-up of anti-spike receptor binding domain (RBD) SARS-CoV-2 antibodies among healthcare workers in Boston, MA

ABSTRACT

Over 15-months we found that anti-spike RBD SARS-CoV-2 antibody concentrations follow different trends with combinations and permutations of COVID-19 infection and vaccination among healthcare workers in Boston, MA. A majority of HCWs remain well above the positivity threshold for anti-spike RBD IgG antibodies for at least 9 months following vaccination regardless of infection history. Of interest, those with COVID-19 infection before vaccination had significantly higher median serum antibody concentrations in comparison to HCWs with no prior infection at each follow-up timepoint. These findings further support what is known regarding the decline in serum antibody concentrations following natural infection and vaccination, adding knowledge of serum antibodies up to 15 months post infection and 11 months post vaccination. ImportanceBoston Medical Center (BMC) is a safety net hospital in Boston and from the initial wave of COVID-19 there has been overwhelming concern about the exposure of healthcare workers to SARS-CoV-2. We conceived a longitudinal study to assess virus exposure and trends in SARS-CoV-2 antibodies amongst healthcare workers at BMC over 15 months. We have followed HCWs through three waves of COVID-19, including the Delta variant wave from June through mid-December 2021, assessing anti-spike receptor binding domain IgG, anti-nucleocapsid IgG, and anti-spike IgM at approximately three-month intervals. Current literature largely describes antibody durability six months post vaccination. These data add to the literature by describing antibody durability and trend differences according to infection history and vaccination status. These longitudinal data contribute to a greater understanding of the ongoing COVID-19 pandemic and can help inform future research and public health decision-making regarding vaccine uptake, breakthrough infections, and overall pandemic response.