Evidence for Aerosol Transfer of SARS-CoV2-specific Humoral Immunity

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Introduction

The vaccines against SARS-CoV-2 have maintained remarkable efficacy against severe disease and death in those vaccinated regardless of variant emergence, Omicron included. Less appreciated than the systemic immunity generated by the vaccines are the high levels of antibody (IgG and IgA) found within the nasal cavity and saliva of vaccinees. This outcome is found in both humans and primates, and in response to both mRNA and protein-based vaccines 2,3. Respiratory transmission of viral infection is proof that oral/nasal cavity constituents can be communicated through aerosols and/or respiratory droplets. As such, it would stand to reason that antibody present within the oral/nasal environment may also be aerosolized to some degree.

Results

The extended mandates for mask wearing in both social and work environments provided a unique opportunity to evaluate the possibility of aerosolized antibody expiration from vaccinated individuals. Utilizing a flow cytometry-based Multiplex Microsphere Immunoassay (MMIA) to detect SARS-CoV-2-specific antibodies (Fig 1A and B) 4,5 and a method previously used to elute antibody from rehydrated dried blood spots (DBS), we identified anti-SARS-CoV-2 specific antibodies eluted from surgical face masks worn by vaccinated lab members donated at the end of one workday. Consistent with the results reported by others, we identified both IgG and IgA in saliva from vaccinated individuals (Fig 1C and D). It was therefore not surprising to detect both IgG and IgA following elution of antibody from face masks (Fig 1C and D). Given these observations, we hypothesized that droplet/aerosolized antibody transfer might occur between individuals, much like droplet/aerosolized virus particles can be exchanged by the same route. To evaluate this hypothesis, we obtained nasal swabs from children living in households in which parents or family members had varying degrees of SARS-CoV2-specifc immunity, including those unvaccinated, vaccinated and COVID-19+.

Initial comparison of nasal swabs acquired from children living in vaccinated households revealed readily detectable SARS-CoV-2-specific IgG (Fig 1E), especially when compared to the complete deficit of SARSCoV-2-specific antibody detected in the few nasal swabs we obtained from children in nonvaccinated households. We then used the variation in parents’ levels of intranasal IgG as the basis of stratification across all children’s samples. Log transformation of the data from thirtyfour adult-child pairs established antibody cut-offs for high vs low parental intranasal antibody levels. Evaluation of samples in this fashion revealed that high intranasal IgG in vaccinated parents was significantly associated (p-value = 0.01) with a 0.38 increase in the log transformed It is made available under a CC-BY-NC-ND 4.0 International license . (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.  This significant positive relationship was observed using either parametric or non-parametric analysis, and adjustments for the correlation within household did not alter the conclusion. Though not statistically significant, a similar trend of elevated IgA was found in the same samples.

Discussion

The concept of herd immunity is a central tenant of public health vaccination campaigns. Overt blockade of infection as well as a reduction in viral transmission downstream of a breakthrough infection are widely accepted conceptual mechanisms by which vaccination-induced immunity in specific individuals protects non-immune community members. Our results suggest that aerosol transmission of antibodies may also contribute to host protection and represent an entirely unrecognized mechanism by which passive immune protection may be communicated. Whether antibody transfer mediates host protection will be a function of exposure, but it seems reasonable to suggest, all things being equal, that any amount of antibody transfer would prove useful to the recipient host. A recent publication showed substantial benefits of parental vaccination in reducing the risk of infection in the unvaccinated children in the same home 6 . It is tempting to speculate that aerosol-mediated antibody transfer may have possibly contributed to their findings reported.