Background: With the emergence of novel SARS-CoV-2 variants, surveillance studies assessing infection rates can provide useful information on vaccine effectiveness and guide ongoing vaccination strategies.
Objectives: Describe the rate of SARS-CoV-2 test positivity in the United States based on mRNA-1273 vaccination or no COVID-19 vaccination.
Methods: SARS-CoV-2 test (RT-PCR or antigen) outcomes within the US CVS Health retail pharmacy network test population were collected between 25 April 2021 and 29 January 2022; self-reported demographic, health information, COVID-19 vaccination status, vaccine identity, and primary series completion date were also collected. Test data were analyzed based on vaccination status; breakthrough infections were defined as a positive SARS-CoV-2 test in mRNA-1273–vaccinated individuals ≥14 days after completing the 2-dose primary series. Participants vaccinated with other COVID-19 vaccines were excluded.
Results: Overall, 23,010,347 SARS-CoV-2 tests were performed (unvaccinated, n=9,415,865 [40.9%]; 2-dose mRNA-1273, n=4,132,953 [18.0%]), of which there were 1,412,239 SARS-CoV-2–positive cases (15.0%) in unvaccinated individuals and 332,202 breakthrough cases (8.0%). At the nadir of the pandemic (May 2021), SARS-CoV-2 test positivity rates were 0.6% and 5.7% among mRNA-1273 vaccinated and unvaccinated individuals, respectively. During the delta (July and August 2021) and omicron (December 2021 and January 2022) periods, peak SARS-CoV-2 test positivity rates were 20.4% and 35.1% among unvaccinated individuals, respectively; the corresponding peak breakthrough infection rates were 4.8% and 24.9%, respectively. Notably, for both delta and omicron periods, rapid weekly increases in SARS-CoV-2 test positivity were observed in the weeks preceding the peak.
Conclusions: These findings highlight that increases in SARS-CoV-2 test positivity rates within the US CVS Health retail pharmacy network test population may be a useful predictor for surges in SARS-CoV-2 infections during the COVID-19 pandemic. The higher rate of breakthrough infections during omicron vs delta could indicate higher transmissibility of omicron, waning vaccine effectiveness, or the ability of omicron to evade vaccine-induced immunity. Nevertheless, these data indicate that individuals who completed a 2-dose mRNA-1273 series may be better protected against SARS-CoV-2 infection compared with no vaccination.
