This is a summary, written by members of the CITF Secretariat, of:

Nahass GR, Salomon-Shulman RE, Blacker G, Haider K, Brotherton R, Teague K, Yiu YY, Brewer RE, Galloway SD, Hansen P, Marquez-Arreguin G, Sheikh-Mohamed S, Chao GYC, Isho B, Do E, Chang I, Snow T, Lee AS, STANFORD COVID-19 BIOBANK, Manohar M, Yang S, Blomkalns AL, Rogers AJ, McGeer A, Gingras A-C, Straus S, Grant P, Nadeau KC, Blish CA, Gommerman JL, Sanders EC, Weissman IL, Caspi Tal M. Intramuscular SARS-CoV-2 vaccines elicit varying degrees of plasma and salivary antibody responses as compared to natural infection. medRxiv 2021.08.22.21262168; doi: 10.1101/2021.08.22.21262168

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

Individuals who have recovered from COVID-19 or who have received SARS-CoV-2 vaccines (mRNA or adenovirus-based) have been shown to have virus-neutralizing activity in their saliva. These results appeared in a recent pre-print, therefore not yet peer reviewed, directed by scientists from Stanford University School of Medicine, with contributions from CITF-funded researchers Drs. Jennifer Gommerman, Allison McGeer, Anne-Claude Gingras, and Sharon Straus.

Previous infection or COVID-19 vaccination has been observed to induce antibodies and cellular immune responses in blood. However, blood is not the first site where the immune system encounters the virus. Rather, SARS-CoV-2 is a respiratory virus which spreads primarily via aerosols generated from saliva when an infected person coughs or sneezes and enters new hosts through the mouth or nose. As such, the presence of protective antibodies in saliva could contribute to reducing transmission of the virus.

Key points:

  • COVID-19 recovered individuals, or those who have received SARS-CoV-2 vaccines (either as a single dose of Johnson & Johnson/Janssen or two doses of the Pfizer-BioNTech or Moderna mRNA vaccines) have SARS-CoV-2 specific IgG and IgA antibodies in their saliva.
  • Some of these IgG and IgA antibodies have the potential to neutralize live SARS-CoV-2.
  • Two doses of an mRNA vaccine induced high levels of neutralizing activity in saliva, while a single dose of adenovirus Johnson & Johnson vaccine had almost undetectable levels of neutralizing antibodies.
  • The role of salivary antibodies in the protection against SARS-CoV-2 infection is unknown and merits further investigation.

This CITF-funded group of researchers had previously released another pre-print publication, partially funded by the CITF and led by Dr. Jennifer Gommerman, also suggesting that there may be a modest neutralizing capacity in the saliva of previously infected or vaccinated individuals.