So do antibodies developed do to prior exposure to other coronaviruses offer protection against SARS-CoV-2?
- Paper #1: In 40-60% of a group of individuals not exposed to SARS-CoV-2 (samples collected between 2015-18), T helper cells were reactive to SARS-CoV-2; as the authors note, the most plausible explanation is cross-reactivity due to previous infection with endemic, circulating coronaviruses responsible for the common cold.
- Paper #2: Antibodies from a group of individuals who had been infected with the original SARS virus (2002-04) failed to neutralize SARS-CoV-2. This seems to contradict paper #1 since genetic analysis indicates that these two viruses are closely related. OTOH, these individuals retained immunity to SARS as much as 17 years after initial infection.
- Paper #3: Published on May 18th, this most recent paper shows that at least one monoclonal antibody for SARS (derived from memory B cells of a single individual infected in 2003) effectively neutralizes SARS-CoV-2 (contra paper #2).
These contradictory findings are exactly how science works when there’s a new phenomenon. Uncertainty is to be expected. Every finding is an exciting potential lead, but nothing is etched in stone (yet).
 Grifoni, A., Weiskopf, D., Ramirez, S.I., Mateus, J., Dan, J.M., Moderbacher,
C.R., Rawlings, S.A., Sutherland, A., Premkumar, L., Jadi, R.S., Marrama, D., de Silva, A.M., Frazier, A., Carlin, A., Greenbaum, J.A., Peters, B., Krammer, F., Smith, D.M., Crotty, S., Sette, A., Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals, Cell (2020), doi: https://doi.org/10.1016/j.cell.2020.05.015.
 Anderson DE, Tan CW, Chia WN, et al. Lack of cross-neutralization by SARS patient sera towards SARS-CoV-2. Emerging Microbes & Infections. 2020;9(1):900-902. doi:10.1080/22221751.2020.1761267
 Pinto, D., Park, Y., Beltramello, M. et al. Cross-neutralization of SARS-CoV-2 by a human monoclonal SARS-CoV antibody. Nature (2020). https://doi.org/10.1038/s41586-020-2349-y