A Cross-Sectional Study of SARS-CoV-2 Seroprevalence between Fall 2020 and February 2021 in Allegheny County, Western Pennsylvania, USA

Round 1

Reviewer 1 Report

The authors established spike and N ELISA to distiguish infected and vaccinated people.

 

They detected spike and N antibodies in the serum samples from  Allegheny County and found the postive sample were increased due to the nature infection and vaccination. Their ELISA assay was well designed the conclusions were solid based on their data. Also, there are some interesting findings based on the results, for example, the corelation of NA titer with RBD titer, higher NA titer when RBD and N titer are both positive.

 

These findings are very useful in design vaccine and thus very informative.

Author Response

We appreciate the positive comments from Reviewer 1.

Reviewer 2 Report

This is a very good study on a small group of people. Which is not to diminish it's importance, as all of these types of study contribute to the bigger picture. I also think that all of the data is in place. My concerns are about how the data is presented in the paper and feel that data could be 1) simplified; 2) shown in a different way or 3) moved to/from supplemental data, as the authors prefer.

Figure 1 A and B: the addition of all of the different other infections makes this figure far too complicated for the point raised in the paper. The patients could be combined into an "other diagnosis" column, rather than having them all. The paper does not seek to correlate any of these conditions with the serum results - therefore, the extra information is unnecessary in the main body.

Figure 2 C and D: I am not sure that this validation is correct (Ore rather, that these data are correctly referred to as validating). This was using samples that were positive - but the point is 'do people make antibodies when infected'. So, there could be some patients who are SARS-CoV-2 positive, but do not make detectable antibodies (for a variety of reasons). 

Table 1: The demographic information is important, but could be supplemental data. More interesting would be the seroprevelance in a (or a select number of) group(s).

Figure 3A: too much information is included. Also - can the 'unclear' be characterized as seropositive for either and then assigned to the group as 'putative' infected or vaccinated?

Figures 3B and 3C: As this point is raised in the text: I feel the 'dual positive' individuals should be highlighted somehow.

Finally - I feel statistics are underused and more general phrases used instead. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This is in interesting work analyzing the SARS-CoV-2 seroprevalence between Fall 2020 and February 2021 in Allegheny County,US. More in detail, the authors examined human blood samples taken in the above mentioned periods for spike (S) protein receptor binding domain (RBD) and nucleocapsid protein (N) antibodies. All RBD positive samples underwent further analysis for virus specific neutralization activity. The study found an increase of antibodies in February 2021 due to both to the higher COVID-19 impact during winter and also to the first effects of the vaccination. RBD but not N levels were high in case of vaccinated individuals as the vaccines used in US (mainly RNA-based) lead to S protein (but not N protein) production in vaccinated people. This method is particularly interesting because allows one to distinguish vaccinated (RBD+, N-) from infected (RBD+, N+) individuals.

1-Do you have the possibility to link the RBD level in vaccinated people to the specific vaccine (Pfizer or Moderna) they received? Is there no DNA-based vaccine in use in US? A comment on the possible differences in antibody production (and their levels) by different vaccines could be appreciated by the reader.

2-If RBD level (with N-) is not very high, neutralization of SARS-CoV-2 seems less effective than that found in infected people. The authors mention possible 'qualitative' differences in neutralizing antibodies. Could you please better explain this point? Is not your method able to detect antibodies associated to mutated S proteins? This is a very important point because it is not clear if the RBD+, N- individuals are protected against SARS-CoV-2 as one would expect.

3-higher COVID-19 impacts on American Africans are reported in the literature. The authors should mention it citing at least the work with DOI:10.1007/s40615-020-00897-2

4-a brief mention to COVID-19 drug discovery using repurposed drugs should be made in the revised manuscript citing at least the work with DOI: 10.3390/molecules26040986

5-authors report for their work 'a major strength' but no limitations of their study. Should the number of samples analyzed considered as a limitation?

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf