Thanks for the citation, I hadn't seen that paper yet.

I agree it predominantly speaks to antibody levels. For others reading who don't already know - antibody levels are used as proxy to measure immune protection, but currently there is no scientific consensus that increasingly higher antibody levels correspond to increasingly better protection. Similarly, it is difficult to determine at what antibody levels an individual is "protected enough". So answering those questions is an ongoing scientific endeavor.

With that said, the literature is rapidly approaching (and likely has already established) scientific consensus that vaccination increases many components of the humoral response to SARS-CoV-2 infection. But for the reasons I previously stated, this has not been proven to translate into better protection or additional benefits for previously infected individuals.

So while antibody levels are a useful measure, another important factor is the robustness of the vaccine induced immune responses in comparison to the response induced in naturally infected individuals. There is a relevant section in the paper you cited titled 'mRNA vaccines induce higher Ab levels and greater Ab breadth than natural exposure to infection'.

My takeaway is that the authors are concluding that the vaccine induces a more robust antibody response because "the vaccine induced significant cross-reactive Abs against the SARS spike and SARS RBD". However they also clearly state that the vaccine does not induce antibodies against the nucleocapsid protein, which natural infection does.

For these reasons I feel that characterizing the vaccine induced immune response as "more robust" doesn't really paint an accurate picture. Especially when it has yet to be proven that this difference in immune response is actually beneficial for health outcomes in people infected with the virus.

Here are some key excerpts:

- "The nucleocapsid protein (NP) is an immunodominant antigen for which the antibody response increases in concordance with natural exposure (Figure 2A,3A and 4)."

- "However, nucleocapsid is not a component of the mRNA vaccines and consequently there is no vaccine-induced increase in Ab against this antigen. Accordingly, anti-spike antibody levels increased in vaccinees while the nucleocapsid protein Ab level remained constant."

- "Natural exposure in seropositive people induces high antibody levels against nucleocapsid protein (NP), full-length spike (S1+S2) and the S2 domain. Antibodies against S1 and the RBD domains are lower."

- "Vaccinated individuals have high Ab levels against full-length spike and the S2 domain of SARS-CoV-2 spike, and significantly higher antibody levels against S1 and the RBD domains compared to naturally exposed individuals."

- "In natural exposure there was no significant cross-reactivity against SARS S1 or the RBD domains. Surprisingly, the vaccine induced significant cross-reactive Abs against the SARS spike and SARS RBD."

- "Vaccination induces a more robust antibody response than natural exposure alone, SUGGESTING that those who have recovered from COVID benefit from the vaccination with stronger and broader antibody response."