Combined Impact of Prior SARS-CoV-2 Infection and Vaccination on Antibody Presence

As COVID-19 continues to spread rapidly and vaccine uptake stagnates, questions remain about the amount of SARS-CoV-2 antibodies present in the population induced by either SARS-CoV-2 infection, by a COVID-19 vaccine, or both. The TEXAS Coronavirus Antibody REsponse Survey (CARES) is a statewide seroprevalence program which utilizes the Roche S-test to detect antibodies to the SARS-CoV-2 spike protein and the Roche N-test to detect antibodies to the SARS-CoV-2 nucleocapsid protein, to monitor the combined impact of prior infection and the COVID-19 vaccine. The current sample size having both S- and N-test data and reported vaccination status is 8,846. Participants with prior infection (i.e. N+) and with either partial or full vaccination have the highest proportion of those showing the maximum value of the S-test (80.95% and 83.07%, respectively). Using a permutation test, there is no statistically significant difference between the median S-test value for those that have had prior infection and are partially vaccinated versus those that have had prior infection and are fully vaccinated. These groups both show significantly higher median amount compared to the other three groups: N+/not vaccinated, N-/partially vaccinated, and N-/fully vaccinated (all p-values < 0.0001). Unvaccinated individuals with prior infection have one of the lowest median S-test values. For participants with previous SARS-CoV-2 infection and a COVID-19 vaccine, the median S-test value is high and is not statistically different between those who are partially vaccinated and those who are fully vaccinated.