ABSTRACT
Coronavirus disease 2019 mass vaccination has led to drastic reduction in hospitalizations and mortality. A number of case reports have emerged reporting coronavirus disease 2019 infection within days following vaccination. There is a need to understand development of immune antibodies in the early post-vaccination period. A prospective analysis of immunoglobulin M and immunoglobulin G kinetics was conducted during the first 28 d following vaccination with either CanSino or Sinovac vaccines in a cohort of 40 healthy volunteers. Serial blood samples were collected from the volunteers right before the first dose of vaccine (d 0) and then on d 4, d 7, d 14, d 21, d 24 and d 28 post-vaccination. Using enzyme-linked immunosorbent assay, circulating anti-severe acute respiratory syndrome coronavirus 2 receptor binding domain immunoglobulin M and immunoglobulin G antibodies were analyzed. Most vaccine recipients (31/40) did not develop any circulating immunoglobulin M. The remaining 9 recipients showed a typical immunoglobulin M curve with antibodies appearing on d 4, peaking on d 7 and declining on d 21 and beyond. Immunoglobulin G response was more typical within 38/40 recipients showing the appearance of immunoglobulin G on d 4, which continued till the end of the study period. This study demonstrates that vaccine-induced immunoglobulin M-based immunity cannot be relied during the first few days following vaccination and more time is needed to have a better picture of the real situation.